Federal Motor Vehicle Safety Standards; Roof Crush Resistance; Phase-In Reporting Requirements

Federal RegisterMay 12, 2009

Ask Donna

What actually matters in this document.

Text

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Parts 571 and 585

[Docket No. NHTSA-2009-0093]

RIN 2127-AG51

Federal Motor Vehicle Safety Standards; Roof Crush Resistance; Phase-In Reporting Requirements

AGENCY:

National Highway Traffic Safety Administration (NHTSA), Department of Transportation.

ACTION:

Final rule.

SUMMARY:

As part of a comprehensive plan for reducing the risk of rollover crashes and the risk of death and serious injury in those crashes, this final rule upgrades the agency's safety standard on roof crush resistance in several ways.

First, for the vehicles currently subject to the standard, i.e., passenger cars and multipurpose passenger vehicles, trucks and buses with a Gross Vehicle Weight Rating (GVWR) of 2,722 kilograms (6,000 pounds) or less, the rule doubles the amount of force the vehicle's roof structure must withstand in the specified test, from 1.5 times the vehicle's unloaded weight to 3.0 times the vehicle's unloaded weight. Second, the rule extends the applicability of the standard so that it will also apply to vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds), but not greater than 4,536 kilograms (10,000 pounds). The rule establishes a force requirement of 1.5 times the vehicle's unloaded weight for these newly included vehicles. Third, the rule requires all of the above vehicles to meet the specified force requirements in a two-sided test, instead of a single-sided test, i.e., the same vehicle must meet the force requirements when tested first on one side and then on the other side of the vehicle. Fourth, the rule establishes a new requirement for maintenance of headroom, i.e., survival space, during testing in addition to the existing limit on the amount of roof crush. The rule also includes a number of special provisions, including ones related to leadtime, to address the needs of multi-stage manufacturers, alterers, and small volume manufacturers.

DATES:

If you wish to petition for reconsideration of this rule, your petition must be received by June 26, 2009.

Effective date:

The date on which this final rule amends the CFR is July 13, 2009. The incorporation by reference of a publication listed in the rule is approved by the Director of the Federal Register as of July 13, 2009.

Compliance dates:

Passenger cars and multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less.

This final rule adopts a phase-in of the upgraded roof crush resistance requirements for these vehicles. The phase-in begins on September 1, 2012. By September 1, 2015, all of these vehicles must meet the upgraded requirements, with certain exceptions. Vehicles produced in more than one stage and altered vehicles need not meet the upgraded requirements until September 1, 2016.

Multipurpose passenger vehicles, trucks and buses with a GVWR greater than 2,722 kilograms (6,000 pounds) and less than or equal to 4,536 kilograms (10,000 pounds).

All of these vehicles must meet the requirements beginning September 1, 2016, with certain exceptions. Vehicles produced in more than one stage and altered vehicles need not meet the requirements until September 1, 2017.

ADDRESSES:

If you wish to petition for reconsideration of this rule, you should refer in your petition to the docket number of this document and submit your petition to: Administrator, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., West Building, Washington, DC 20590.

The petition will be placed in the docket. Anyone is able to search the electronic form of all documents received into any of our dockets by the name of the individual submitting the document (or signing the document, if submitted on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the

Federal Register

published on April 11, 2000 (Volume 65, Number 70; Pages 19477-78) or you may visit

http://www.dot.gov/privacy.html.

FOR FURTHER INFORMATION CONTACT:

For non-legal issues, you may call Christopher J. Wiacek, NHTSA Office of Crashworthiness Standards, telephone 202-366-4801. For legal issues, you may call J. Edward Glancy, NHTSA Office of Chief Counsel, telephone 202-366-2992. You may send mail to these officials at the National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., West Building, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary

a. Final Rule

b. How This Final Rule Differs From the NPRM and/or SNPRM

II. Overall Rollover Problem and the Agency's Comprehensive Response

a. Prevention

b. Occupant Containment

c. Occupant Protection

III. The Role of Roof Intrusion in the Rollover Problem

IV. The Agency's Proposed Rule

a. NPRM

b. SNPRM

c. Congressional Mandate

V. Overview of Comments

VI. Agency Decision and Response to Comments

a. Primary Decisions

1. Basic Nature of the Test Requirements—Quasi-Static vs. Dynamic Tests

2. Vehicle Application

3. Single-Sided or Two-Sided Tests

4. Upgraded Force Requirement—Specified Strength to Weight Ratio (SWR)

5. Performance Criteria—Headroom, Platen Travel, or Both

6. Leadtime and Phase-In

b. Aspects of the Test Procedure

1. Tie-Down Procedure

2. Platen Angle and Size

3. Testing Without Windshields and/or Other Glazing in Place

4. Deletion of Secondary Plate Positioning Procedure

5. Removal of Roof Components

6. Tolerances

c. Requirements for Multi-Stage and Altered Vehicles

d. Other Issues

1. Convertibles and Open Bodied Vehicles

2. Vehicles Without B-Pillars

3. Heavier Vehicles With a High Height to Width Aspect Ratio

4. Active Roofs

5. Whether an Additional SNPRM Is Needed

6. Rear Seat Occupants

7. New Car Assessment Program (NCAP)

8. Possible Energy Requirement

9. Advanced Restraints

VII. Costs and Benefits

VIII. Rulemaking Analyses and Notices

Appendix A—Analysis of Comments Concerning Dynamic Testing

Appendix B—Two-Sided Test Results

Appendix C—Single-Sided Test Results

I. Executive Summary

a. Final Rule

As part of a comprehensive plan for reducing the serious risk of rollover crashes and the risk of death and serious injury in those crashes, this final rule upgrades Federal Motor Vehicle Safety Standard (FMVSS) No. 216,

Roof Crush Resistance.

For the vehicles currently subject to the standard, passenger cars and multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less, the rule doubles the amount of force the vehicle's roof structure must withstand in the specified test, from 1.5 times the

vehicle's unloaded weight to 3.0 times the vehicle's unloaded weight. The rule also extends the applicability of the standard so that it will also apply to vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds), but not greater than 4,536 kilograms (10,000 pounds), establishing a force requirement of 1.5 times the vehicle's unloaded weight for these heavier vehicles.

Under today's rule, all of the above vehicles must meet the specified force requirements in a two-sided test instead of a single-sided test, i.e., the same vehicle must meet the force requirements when tested first on one side and then on the other side of the vehicle. The rule also establishes a new requirement for maintenance of headroom, i.e., survival space, during testing, in addition to the existing limit on the amount of roof crush. The rule also includes special provisions to address the needs of multi-stage manufacturers, alterers, and small volume manufacturers.

NHTSA developed its proposal to upgrade roof crush resistance requirements after considerable analysis and research, including considering comments received in response to a Request for Comments (RFC) notice published in 2001. Prior to publishing the RFC, the agency conducted a research program to examine potential methods for improving the roof crush resistance requirements. The agency testing program included full vehicle dynamic rollover testing, inverted vehicle drop testing, and comparing inverted vehicle drop testing to a modified FMVSS No. 216 test. After considering the results of the testing and other available information, the agency concluded that the quasi-static procedure provides a suitable representation of the real-world dynamic loading conditions, and the most appropriate one on which to focus our upgrade efforts.

Today's rule reflects careful consideration of comments we received in response to the notice of proposed rulemaking (NPRM) published in 2005 and a supplemental notice of proposed rulemaking (SNPRM) published in January 2008. NHTSA published the SNPRM to obtain public comment on a number of issues that might affect the content of the final rule, including possible variations in the proposed requirements. In the SNPRM, the agency also announced the release of the results of various vehicle tests conducted since the NPRM.

While this rulemaking action to improve roof strength is part of our comprehensive plan for addressing the serious problem of rollover crashes, this action, by itself, addresses a relatively small subset of that problem. There are more than 10,000 fatalities in rollover crashes each year. To address that problem, our comprehensive plan includes actions to (1) reduce the occurrence of rollovers, (2) mitigate ejection, and (3) enhance occupant protection when rollovers occur (improved roof crush resistance is included in this third category).

Our analysis shows that of the more than 10,000 fatalities that occur in rollover crashes each year, roof strength is relevant to only about seven percent (about 667) of those fatalities. We estimate that today's rule will prevent 135 of those 667 fatalities.

The portions of our comprehensive plan that will have the highest life-saving benefits are the ones to reduce the occurrence of rollovers (

prevention

) and to mitigate ejection (

occupant containment

). We estimate that by preventing rollovers, electronic stability control (ESC) will reduce the more than 10,000 fatalities that occur in rollover crashes each year by 4,200 to 5,500 fatalities (and also provide significant additional life-saving benefits by preventing other types of crashes). In the area of mitigating ejection, significant life-benefits are and/or will occur by our continuing efforts to increase seat belt use and our upcoming rulemaking on ejection mitigation. A more complete discussion of our comprehensive plan is discussed later in this document.

b. How This Final Rule Differs From the NPRM and/or SNPRM

The more noteworthy changes from the NPRM are outlined below and explained in detail later in this preamble. More minor changes are discussed in the appropriate sections of this preamble.

Higher force requirement (strength-to-weight ratio (SWR level)).

While we proposed an SWR level of 2.5 in the NPRM for the vehicles that have been subject to the standard, we noted in the SNPRM that the agency could adopt a higher or lower value for this final rule. We are adopting an SWR of 3.0 for them in this final rule. An SWR of 1.5 will apply to the heavier light vehicles that have previously not been subject to the standard.

Two-sided test.

While we proposed a single-sided test in the NPRM, we conducted additional testing and addressed the possibility of a two-sided test in the SNPRM. Today's rule adopts a two-sided test requirement for all vehicles subject to the standard.

Maintaining intrusion limit in addition to new headroom requirement.

In the NPRM, we proposed to replace the current limit on intrusion (platen travel requirement) with a new headroom requirement. For this final rule, we are maintaining the intrusion limit as well as adopting the proposed headroom requirement.

Use of headform positioning fixture instead of a test dummy.

In the NPRM, we proposed to use test dummies as part of the test procedure for measuring headroom. For this final rule, we are using headform positioning fixtures for this purpose.

Phase-in.

We did not include a phase-in in the NPRM. For this final rule, we are phasing in the upgraded roof strength requirements for the lighter vehicles previously subject to FMVSS No. 216, and providing longer leadtime (without a phase-in) for the heavier light vehicles.

Limited exclusion for certain multi-stage trucks.

Due to concerns about practicability, we are excluding from FMVSS No. 216 a very limited group of multistage trucks with a GVWR greater than 2,722 kilograms (6,000 pounds), ones not built on either a chassis cab or an incomplete vehicle with a full exterior van body.

Updated benefits and costs.

We have updated our analysis of benefits and costs. Our analysis appears in summary form in this document, and in its entirety in the agency's Final Regulatory Impact Analysis (FRIA).

We estimate that the changes in FMVSS No. 216 will prevent 135 fatalities and 1,065 nonfatal injuries annually. The agency estimates that compliance with the upgraded roof strength standard will increase lifetime consumer costs by $69-114 per affected vehicle. Redesign costs are expected to increase affected vehicle prices by an average of about $54. Added weight is estimated to increase the lifetime cost of fuel usage by $15 to $62 for an average affected vehicle. Total consumer costs are expected to range from $875 million to $1.4 billion annually.

Implied Preemption.

We have reconsidered the tentative position presented in the NPRM. We do not foresee any potential State tort requirements that might conflict with today's final rule. Without any conflict, there could not be any implied preemption.

II. Overall Rollover Problem and the Agency's Comprehensive Response

Addressing vehicle rollovers is one of NHTSA's highest safety priorities. According to 2007 FARS crash data, 10,196 people were killed as occupants

in light vehicle rollover crashes, which represents 35 percent of all occupants killed that year in crashes. FARS reported that approximately 57 percent were partially or completely ejected from the vehicle (including approximately 47 percent who were completely ejected).

Rollover crashes are complex and chaotic events. Rollovers can range from a single quarter turn to eight or more quarter turns, with the duration of the rollover crash lasting from one to several seconds. The wide range of rollover conditions occurs because these crashes largely occur off road where the vehicle motion is highly influenced by roadside conditions. Also, rollover crashes tend to occur at higher speeds than other crash types due to the energy required to initiate the rollover motion.

NHTSA has been pursuing a comprehensive and systematic approach towards reducing the fatalities and serious injuries that result from rollover crashes. As part of our safety standard rulemaking, this approach establishes various repeatable test procedures and performance requirements that will generate countermeasures effective in the chaotic real-world events. Due to the complex nature of a rollover event and the particularized effect of each element of the comprehensive approach taken by the agency to address these crashes, each element addresses a specific segment of the total rollover problem. Accordingly, each initiative has a different target population and interacts with each of the other rollover strategies. NHTSA has initiatives in place to:

1. Reduce the occurrence of rollover crashes (e.g., the requirement for ESC on all light vehicles and the NCAP rollover ratings),

2. Keep occupants inside the vehicle when rollovers occur (e.g., NHTSA's unyielding commitment to get passengers to buckle their seat belts every time they ride in a vehicle, as well as the requirement for enhanced door latches and the forthcoming rulemaking for ejection mitigation), and

3. Better protect the occupants kept inside the vehicle during the rollover (e.g., the requirement for upper interior head protection and this rulemaking for enhanced roof crush resistance).

Each of these three initiatives must work together to address the various aspects of the rollover problem.

a. Prevention

The most effective way to reduce deaths and injuries in rollover crashes is to prevent the rollover crash from occurring. On April 6, 2007, NHTSA published a final rule establishing FMVSS No. 126, “Electronic stability control systems,” to require ESC on passenger cars, multipurpose passenger vehicles, trucks, and buses with a GVWR of 4,536 kilograms (10,000 pounds) or less. ESC systems use automatic computer-controlled braking of individual wheels to assist the driver in maintaining control in critical driving situations in which the vehicle is beginning to lose directional stability at the rear wheels or directional control at the front wheels. ESC systems effectively monitor driver steering input and limit vehicle oversteer and understeer, as appropriate. To comply with the new ESC standard, vehicles will need individually adjustable braking at all four wheels, and computer electronics to utilize this capability, a means for engine torque adjustability and various onboard sensors (to measure yaw rate, lateral acceleration, steering wheel angle and speed). The agency estimates that ESC will save 5,300 to 9,600 lives in all types of crashes annually once all light vehicles on the road are equipped with ESC. The agency further anticipates that ESC systems will substantially reduce (by 4,200 to 5,500 deaths) the more than 10,000 deaths each year resulting from rollover crashes.

b. Occupant Containment

Studies have shown that the fatality rate for an ejected vehicle occupant is three times as great as that for an occupant who remains inside of the vehicle. Thus, mitigating ejections offers potential for significant safety gains. Safety belts are the most effective crashworthiness countermeasure in reducing ejected rollover fatalities. Studies have found that safety belts reduce fatalities in rollovers by 74 percent in passenger cars and 80 percent for light trucks.

NHTSA requires all vehicles manufactured after 1968 to have safety belts as standard equipment.

Kahane, C. J., Fatality Reduction by Safety Belts for Front-Seat Occupants of Cars and Light Trucks: Updated and Expanded Estimates Based on 1986-99 FARS Data (NHTSA Report No. DOT HS 809 199).

However, of the 6,164 ejected occupant fatalities in light vehicle rollover crashes, as reported by 2006 FARS, 1,135 were classified as partial ejections. Fatal injuries from partial ejection can occur even to belted occupants, e.g., when their head protrudes outside the window and strikes the ground in a rollover. Therefore, as mandated by SAFETEA-LU, NHTSA is working to establish performance standards to reduce partial and complete ejection from outboard seating position windows.

Doors represent another common ejection route. As part of the agency's comprehensive approach to rollover, and to harmonize with the first Global Technical Regulation, NHTSA upgraded FMVSS No. 206, “Door locks and door retention components,” in a final rule published on February 6, 2007. This final rule added test requirements for sliding doors, upgraded the door retention requirements, added secondary latch requirements for doors other than hinged side doors and back doors, and provided a new test procedure for assessing inertial forces. To comply with the new requirements, it is anticipated that passenger vehicles with sliding doors designed with one latch and pin locking mechanism will need to be redesigned with two latches. The technology needed to meet the upgraded standard would benefit vehicles in rollover crashes where door openings were identified as a problem.

c. Occupant Protection

Finally, when a rollover crash does occur and the occupants have been contained within the vehicle compartment, it is important for the roof structure to remain intact and maintain survival space. That is the safety need addressed by today's final rule.

III. The Role of Roof Intrusion in the Rollover Problem

Due to the high effectiveness of ESC in preventing an increasing number of rollover crashes, and seat belts at preventing ejection, the remaining target population relevant to roof crush occupant protection is a relatively small subset of the occupants injured in rollovers. For fatalities, the estimated total for the target population

is about seven percent (about 667) of all non-convertible light vehicle rollover fatalities. Although the target population and potential for lives saved are substantially smaller than can be attained by the first two strategies of our comprehensive rollover plan, it is nevertheless a very important aspect of the plan.

The target population estimates were based upon the results from the 1997-2006 National Automotive Sampling System-Crashworthiness Data System (NASS-CDS).

Looking at the target population relevant to roof crush occupant protection more specifically, Table 1 below shows a breakdown of the target population that could potentially benefit from roof crush improvements. The target population for all light vehicles is stratified by injury severity. The injury mechanism due to roof crush for belted occupants is that the roof crushes during the roll event, intrudes

into the occupant compartment, and causes head, face, or neck injury. The table demonstrates how the final target population is derived from the broad category of rollovers by eliminating cases in which roof strength improvements would not be effective in reducing serious and fatal injuries. For example, a stronger roof would not be expected to provide benefits in cases where the roof was not involved; where the occupant was totally ejected from the vehicle,

or where the most serious injury was not to the head, neck, or face due to the intruding roof.

Strashny, “The Role of Vertical Roof Intrusion in Predicting Occupant Ejection,” 2009. Strashny found that there was no statistically significant relationship between the level of roof intrusion and the probability of complete ejection. For this reason completely ejection occupants were excluded from the target population. However, partial ejections that meet the established criteria are included.

The final target populations are shown in bold at the bottom of the table. A full discussion of the basis for the target population is included in the FRIA.

Table 1—Target Population Potentially Affected by Improved Roof Strength

AIS 1

AIS 2

AIS 3-5

Fatalities

All Light Vehicles

All Vehicles:

Non-Convertible Light Vehicles in Rollovers

199,822

37,305

21,673

10,150

Roof-Involved Rollover

164,213

32,959

19,262

8,645

Some Fixed Object Collision on Top

153,520

29,419

17,766

7,559

Not Totally Ejected

149,850

26,033

12,355

3,654

Using Safety Restraints

116,670

14,327

8,970

2,096

Outboard Seats

115,018

14,241

8,781

2,096

Roof Component Intrusion

68,730

10,922

6,842

1,444

Head, Neck, or Face Injury From Intruding Roof Component

24,035

6,580

2,993

957

Injury—Not MAIS

−1,900

−1,252

−237

Injury at MAIS—Not Sole Injury

−17,818

−292

−253

−53

Sole MAIS Injury

6,216

4,388

1,487

667

Light Vehicles With a GVWR of 2,722 Kilograms (6,000 Pounds) or Less

PC & LT < 6,000 lbs:

Non-Convertible Light Vehicles in Rollovers

172,846

33,170

18,929

8,719

Roof-Involved Rollover

144,410

29,098

17,360

7,536

Some Fixed Object Collision on Top

136,080

26,270

16,122

6,484

Not Totally Ejected

133,241

23,400

11,406

3,142

Using Safety Restraints

104,571

12,421

8,379

1,936

Outboard Seats

103,249

12,373

8,190

1,936

Roof Component Intrusion

60,061

9,370

6,372

1,304

Head, Neck, or Face Injury From Intruding Roof Component

20,687

5,868

2,615

842

Injury—Not MAIS

−1,771

−1,119

−157

Injury at MAIS—Not Sole Injury

−16,082

−262

−212

−50

Sole MAIS Injury

4,605

3,835

1,283

635

Light Vehicles With a GVWR above 2,722 Kilograms (6,000 Pounds)

LT > 6,000 lbs:

Non-Convertible Light Vehicles in Rollovers

26,975

4,135

2,744

1,431

Roof-Involved Rollover

19,803

3,861

1,902

1,110

Some Fixed Object Collision on Top

17,440

3,149

1,644

1,075

Not Totally Ejected

16,608

2,634

949

511

Using Safety Restraints

12,099

1,906

591

160

Outboard Seats

11,770

1,868

591

160

Roof Component Intrusion

8,669

1,552

471

140

Head, Neck, or Face Injury From Intruding Roof Component

3,348

712

378

116

Injury—Not MAIS

−128

−133

−80

Injury at MAIS—Not Sole Injury

−1,736

−31

−40

−3

Sole MAIS Injury

1,611

553

205

The most

significant exclusions resulted from requirements that fatalities occurred in rollovers in which (1) the roof was damaged in a rollover, (2) the damage was not caused by collision with a fixed object, (3) the fatally injured occupants were not ejected, and (4) those occupants were belted.

Note: The relevant target population used for the estimation of benefits is identified in the row titled “Sole MAIS Injury.” Also, the numbers reflect rounding errors.

Injury—Not MAIS: This means that the most serious injury was to a portion of the body other than the head, neck or face.

It is important to understand what Table 1 indicates about the safety

potential of addressing roof crush. Even if there were some way to prevent every single rollover death resulting from roof crush, the total lives saved would be 667, not the approximately 10,000 deaths that result from rollover each year. This is why each initiative in NHTSA's comprehensive program to address the different aspects of the rollover problem is so important.

The details of today's rule upgrading roof crush occupant protection, including costs and benefits and the agency's analysis of the public comments on our NPRM and SNPRM, are discussed in the rest of this document.

IV. The Agency's Proposed Rule

a. NPRM

On August 23, 2005, NHTSA published in the

Federal Register

(70 FR 49223) a NPRM to upgrade FMVSS No. 216,

Roof Crush Resistance.

FMVSS No. 216 seeks to reduce deaths and serious injuries resulting from the roof being crushed and pushed into the occupant compartment when the roof strikes the ground during rollover crashes.

Docket No. NHTSA-2005-22143.

Current requirements.

FMVSS No. 216 currently applies to passenger cars, and to multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less.

The standard requires that when a large steel test plate (sometimes referred to as a platen) is placed in contact with the roof of a vehicle and then pressed downward, simulating contact of the roof with the ground during a rollover crash, with steadily increasing force until a force equivalent to 1.5 times the unloaded weight of the vehicle is reached, the distance that the test plate has moved from the point of contact must not exceed 127 mm (5 inches). The criterion of the test plate not being permitted to move more than a specified amount is sometimes referred to as the “platen travel” criterion. Under S5 of the standard, the application of force is limited to 22,240 Newtons (5,000 pounds) for passenger cars, even if the unloaded weight of the car times 1.5 is greater than that amount.

Proposed upgrade

As discussed in the August 2005 NPRM, we developed our proposal to upgrade roof crush resistance requirements after considerable analysis and research, including considering comments received in response to a RFC published in the

Federal Register

(66 FR 53376)

on October 22, 2001. Prior to publishing the RFC, the agency conducted a research program to examine potential methods for improving the roof crush resistance requirements. The agency testing program included full vehicle dynamic rollover testing, inverted vehicle drop testing, and comparing inverted drop testing to a modified FMVSS No. 216 test. After considering the results of the testing and other available information, the agency concluded that the quasi-static procedure provides a suitable representation of the real-world dynamic loading conditions, and the most appropriate one on which to focus our upgrade efforts.

Docket No. NHTSA-1999-5572.

In our August 2005 NPRM, to better address fatalities and injuries occurring in roof-involved rollover crashes, we proposed to extend the application of the standard to vehicles with a GVWR of up to 4,536 kilograms (10,000 pounds), and to strengthen the requirements of FMVSS No. 216 by mandating that the vehicle roof structures withstand a force equivalent to 2.5 times the unloaded vehicle weight, and to eliminate the 22,240 Newton (5,000 pound) force limit for passenger cars.

Further, in recognition of the fact that the pre-test distance between the interior surface of the roof and a given occupant's head varies from vehicle model to vehicle model, we proposed to regulate roof strength by requiring that the crush not exceed the available headroom. Under the proposal, this requirement would replace the current limit on test plate movement.

The proposed new limit would prohibit any roof component from contacting the head of a seated 50th percentile male dummy when the roof is subjected to a force equivalent to 2.5 times the unloaded vehicle weight. We note that this value is sometimes referred to as the strength-to-weight ratio (SWR), e.g., a SWR of 1.5, 2.5, and so forth.

We also proposed to:

• Allow vehicles manufactured in two or more stages, other than chassis-cabs, to be certified to the roof crush requirements of FMVSS No. 220,

School bus rollover protection,

instead of FMVSS No. 216.

• Clarify the definition and scope of exclusion for convertibles.

• Revise the vehicle tie-down procedure to minimize variability in testing.

To accompany our proposal, we prepared a Preliminary Regulatory Impact Analysis (PRIA) describing the costs and benefits. We estimated that, if adopted, the proposal would result in 13-44 fewer fatalities and 498-793 fewer non-fatal injuries each year. The total estimated recurring fleet cost was $88 to $95 million. We estimated that approximately 32 percent of the current vehicle fleet would need improvements to meet the proposed upgraded requirements.

b. SNPRM

On January 30, 2008, NHTSA published in the

Federal Register

(73 FR 5484) an SNPRM for our ongoing roof crush resistance rulemaking.

In that document, we asked for public comment on a number of issues that might affect the content of the final rule, including possible variations in the proposed requirements. We also announced the release of the results of various vehicle tests conducted since the proposal.

Docket No. NHTSA-2008-0015.

In the SNPRM, we noted that we had been carefully analyzing the numerous comments we had received on the NPRM, as well as the various additional vehicle tests, including both single-sided tests and two-sided tests, conducted since the NPRM. We invited comments on how the agency should factor the new information into its decision. We noted that while the NPRM focused on a specified force equivalent to 2.5 times the unloaded vehicle weight, the agency could adopt a higher or lower value for the final rule. We explained, with respect to two-sided testing, that we believed there was now sufficient available information for the agency to consider a two-sided requirement as an alternative to the single-sided procedure described in the NPRM. We stated that we planned to evaluate both the single-sided and two-sided testing alternatives for the final rule and requested comments that would help us reach a decision on that issue.

We also noted in the SNPRM that the agency had conducted additional analysis concerning the role of vertical roof intrusion and post-crash headroom in predicting roof contact injuries to the head, neck or face during FMVSS No. 216 rollovers. At the time of the NPRM, the agency estimated benefits based on post-crash headroom, the only basis for which a statistical relationship with injury reduction had been established. After the NPRM, with additional years of data available, a statistically significant relationship between intrusion and injury for belted occupants was established.

c. Congressional Mandate

Section 10301 of SAFETEA-LU generally required the Secretary to issue

a final rule upgrading roof crush resistance by July 1, 2008, while providing for a later date under certain circumstances. That section provides:

Sec. 10301. VEHICLE ROLLOVER PREVENTION AND CRASH MITIGATION.

(a) In General.—Subchapter II of chapter 301 is amended by adding at the end the following:

§ 30128. Vehicle rollover prevention and crash mitigation

(a) IN GENERAL.—The Secretary shall initiate rulemaking proceedings, for the purpose of establishing rules or standards that will reduce vehicle rollover crashes and mitigate deaths and injuries associated with such crashes for motor vehicles with a gross vehicle weight rating of not more than 10,000 pounds.

(d) Protection of Occupants.—One of the rulemaking proceedings initiated under subsection (a) shall be to establish performance criteria to upgrade Federal Motor Vehicle Safety Standard No. 216 relating to roof strength for driver and passenger sides. The Secretary may consider industry and independent dynamic tests that realistically duplicate the actual forces transmitted during a rollover crash. The Secretary shall issue a proposed rule by December 31, 2005, and a final rule by July 1, 2008.

The statute provides that if the Secretary determines that the July 1, 2008 deadline for the final rule cannot be met, the Secretary is to notify Congress and explain why that deadline cannot be met, and establish a new date. The Secretary provided such notifications to Congress, and established a date of April 30, 2009.

V. Overview of Comments

NHTSA received comments from a wide variety of interested parties, including vehicle manufacturers and their trade associations, suppliers of automobile equipment and a supplier trade association, consumer advocacy and other organizations, trial lawyers, engineering firms and consultants, members of academia, elected officials and government organizations, and private individuals. All of the comments may be found in the docket for the NPRM or SNPRM. In this section, we provide a broad overview of the significant comments. Where we identify specific commenters, we cite representative comments.

General Approach and SWR

Vehicle manufacturers were generally supportive of the agency's proposal, while recommending a number of specific modifications. They generally supported a SWR of 2.5, with caveats about sufficient leadtime and test procedure issues. They expressed concerns about SWRs higher than 2.5, including potential adverse effects on safety resulting from increased mass.

Consumer advocacy organizations and a number of other commenters argued that it is not enough to upgrade the current quasi-static requirement, and that a dynamic test requirement is needed. While specific recommendations varied, one was for the agency to adopt an upgraded quasi-static requirement now, and to proceed with further rulemaking for a dynamic test.

Advocates for Highway Safety (Advocates) stated that the proposed quasi-static test cannot demonstrate actual roof crush resistance in rollover crashes and that a dynamic test would address occupant kinematics and injury responses in actual rollover crashes. Public Citizen stated that a dynamic test could simultaneously evaluate the performance of seat belts, doors, ejection and the roof. A number of commenters supported specific dynamic tests.

The Center for Auto Safety (CAS) stated that while it strongly supports a dynamic test, it believes rollover protection can be dramatically improved with a well-crafted quasi-static test. It argued that test procedure changes related to roll angle and pitch angle are needed to ensure that the roof receives appropriate shear stress.

As to the SWR for an upgraded quasi-static test requirement, consumer advocacy organizations and a number of other commenters argued that the SWR should be significantly higher than 2.5. Many of these commenters recommended a SWR of 3.5, with some recommending higher levels.

The Insurance Institute for Highway Safety (IIHS) submitted a new study which it said supports increasing the SWR beyond 2.5. It stated that based on the current evidence, it supports a SWR of 3.0 to 3.5.

Performance Criterion

The agency received a variety of comments on the proposed headroom reduction criterion. Some commenters, including consumer groups, supported a headroom reduction criterion but argued that a platen travel criterion is also needed. Several commenters expressed concern that, for some vehicles, the proposed headroom reduction criterion would be less stringent and less protective than the current platen travel criterion. The agency also received comments recommending that the agency make these criteria more stringent to protect taller occupants, e.g., by using a 95th percentile adult male dummy instead of a 50th percentile adult male dummy to measure headroom and by reducing the amount of platen travel that is permitted.

Vehicle manufacturers urged the agency to retain the current platen travel criterion instead of adopting a headroom reduction criterion. They argued, among other things, that using the headroom reduction criterion would add unnecessary complexity to the test procedure and result in problems related to repeatability and practicability. Some manufacturers stated that if the agency adopts a headroom reduction criterion, it should adopt a test procedure using a head positioning fixture instead of a test dummy.

IIHS stated that relating the allowable amount of roof crush in the quasi-static test to the headroom in specific vehicles is a good concept but that, in practice, the agency's research tests have not shown that replacing the 5-inch platen travel criterion with the headroom requirement would be a meaningful change to the standard and may not justify the added complications to the test procedure.

Single- or Two-Sided Testing

Several consumer advocacy organizations and other commenters strongly supported two-sided testing. Public Citizen stated that in a vast majority of rollover cases, the injured party was typically seated on the far side, that is, the side of the second impact. It argued that it is not possible to upgrade FMVSS No. 216 without a two-sided test requirement.

IIHS stated that while it supports any changes that would increase the level of roof strength of the vehicle fleet, it has no real-world data to address the potential benefits of two-sided testing. It stated that a single-sided test with a higher SWR may be more effective at promoting robust roof designs than a two-sided test with a lower SWR requirement.

The comments of vehicle manufacturers were somewhat mixed on the issue of single- or two-sided testing. The Alliance of Automobile Manufacturers (Alliance) stated that it believes the agency has provided insufficient justification for two-sided testing. It stated that the agency has not provided analysis demonstrating that two-sided testing relates to real-world safety. The Alliance also expressed concern that two-sided testing would amplify variability and repeatability problems.

The Association of International Automobile Manufacturers (AIAM) stated that based on the information and

analysis provided by the agency regarding the two-sided test, it believes that the test shows enough potential to merit further consideration by the agency. AIAM argued that additional analysis would be needed before it could provide a preferred regulatory approach, but indicated that the two-sided approach would more directly address the multiple roof contact weakening phenomenon.

Leadtime

Vehicle manufacturers argued that a phase-in is needed for the upgraded roof crush requirements. The Alliance stated that if the final rule reflected a reasonable accommodation of the issues raised in its comments, it would be reasonable for a phase-in to begin, with a compliance percentage of 20 percent, on the first September 1, that occurred more than 36 months after issuance of the final rule. That organization stated that it would not be practicable to apply the upgraded requirements to all new vehicles at once, since far more vehicle models require redesigns than anticipated by NHTSA. The Alliance requested a phase-in that incorporates carryforward credits. It stated that additional leadtime would be necessary if the agency adopted a head contact criterion instead of platen travel, a two-sided test or a SWR higher than 2.5.

Costs and Benefits

Many commenters addressed the PRIA, which analyzed the costs and benefits and other impacts of the proposed rule, and a later discussion of these impacts included in the SNPRM. Among other things, commenters addressed the target population, the pass/fail rate of the current fleet, cost and weight impacts, and estimates of benefits.

Preemption

We received numerous comments on our discussion in the NPRM of the possible preemptive effect of an upgraded roof crush standard on State common law tort claims. Vehicle manufacturers and one organization strongly supported the view that an upgraded roof crush standard would conflict with and therefore impliedly preempt State rules of tort law imposing more stringent requirements than the one ultimately adopted by NHTSA. Consumer advocacy groups, members of Congress and State officials, trial lawyers, consultants, members of academia, and private individuals strongly opposed that view. The opposing comments from State officials included one signed by 27 State Attorneys General and the National Conference of State Legislatures.

Other Issues

We received comments on many other issues. Commenters addressed a number of issues concerning the FMVSS No. 216 test procedure, including the vehicle tie-down procedure, platen angle and size, and whether the vehicle should be tested with the windshield and/or other glazing in place. Commenters also addressed requirements for multi-stage vehicles.

June 2008 Congressional Hearing and Letters

On June 4, 2008. the Subcommittee on Consumer Affairs, Insurance, and Automotive Safety of the Senate Commerce, Science and Transportation Committee held an oversight hearing on passenger vehicle roof strength. Former NHTSA Deputy Administrator James Ports testified at the hearing. At the hearing and also in a subsequent letter to Secretary Peters dated June 19, 2008, several Senators encouraged the agency to extend the July 1, 2008 date for completing a final rule. They encouraged the agency to ensure a rulemaking that would maximize vehicle safety and significantly reduce deaths and injuries for drivers and passengers in vehicle rollover crashes.

Several Senators encouraged NHTSA to consider a two-sided test requirement and a higher SWR requirement than the proposed 2.5 level, and to provide detailed information concerning alternatives considered by the agency. They also raised concerns about the use of 50th percentile adult male test dummies instead of ones representing taller occupants. The Senators also expressed significant concerns about possible preemption of common law tort actions, and asked that such a provision not be included in the final rule.

In a letter to Secretary Peters dated June 27, 2008, Chairman Henry Waxman of the House Committee on Oversight and Government Reform, raised similar concerns to those of the Senators.

New IIHS Roof Strength Consumer Information Program

On February 19, 2009, IIHS met with NHTSA representatives to provide the agency information about a new roof strength consumer information program that the organization is initiating. IIHS believes the FMVSS No. 216 test procedure is a meaningful structural assessment of real-world rollover crashworthiness as shown by recent studies it has conducted showing that improved roof strength reduces injury risk in midsize SUVs and small cars. That organization indicated that the boundary for a good rating in the IIHS program will be a SWR of 4.0 in a one-sided platen test similar to the existing FMVSS No 216 test procedure. IIHS indicated that it does not plan to rate the larger, heavier light vehicles, i.e., ones likely to have GVWRs greater than 2,722 kilograms (6,000 pounds).

On March 24, 2009, IIHS issued a press release announcing a number of details about its new rating system, including ratings for 12 small SUVs. For an acceptable rating, the minimum SWR is 3.25. A marginal rating value is 2.5. Anything lower than that is rated as poor. In order to earn IIHS's “top safety pick” award for 2010, vehicles will need to have a good roof strength rating, i.e., SWR of 4.0. Of the 12 small SUVs tested by IIHS, eight were rated by that organization as good, five as acceptable, two as marginal, and one as poor.

VI. Agency Decision and Response to Comments

a. Primary Decisions

1. Basic Nature of the Test Requirements—Quasi-Static vs. Dynamic Tests

As noted above and discussed in detail in the NPRM, we developed our proposal to upgrade roof crush resistance requirements after considerable analysis and research, including conducting a research program to examine potential methods for improving the roof crush resistance requirements. The agency testing program included full vehicle dynamic rollover testing, inverted vehicle drop testing, and comparing inverted drop testing to a modified FMVSS No. 216 test. After considering the results of the testing and other available information, the agency concluded that the quasi-static procedure provides a suitable representation of the real-world dynamic loading conditions, and the most appropriate one on which to focus our upgrade efforts.

We did not propose a dynamic test procedure in either the NPRM or the SNPRM. We did discuss in the NPRM a number of types of dynamic tests and why we were not including them in the proposal. We stated our belief that the current quasi-static test procedure is repeatable and capable of simulating real-world deformation patterns. We also stated that we were unaware of any dynamic test procedure that provides a sufficiently repeatable test environment.

Consumer advocacy organizations and a number of other commenters argued that it is not enough to upgrade the current quasi-static requirement, and

that a dynamic test requirement is needed. While specific recommendations varied, one was for the agency to adopt an upgraded quasi-static requirement now, and to proceed with further rulemaking at this time for a dynamic test.

Advocates stated that the proposed quasi-static test cannot demonstrate actual roof crush resistance in rollover crashes and that a dynamic test would address occupant kinematics and injury responses in actual rollover crashes. Public Citizen stated that a dynamic test could simultaneously evaluate the performance of seat belts, doors, ejection mitigation and the roof. A number of commenters made specific recommendations concerning the type of dynamic test that the agency should propose, e.g., with a number recommending the FMVSS No. 208 dolly test and/or the Jordan Rollover System (JRS) test.

As part of our considering the merits of a dynamic test and comments on the JRS, on February 23, 2007, NHTSA representatives met with Xprts, LLC (Xprts) at its test facility in Goleta, CA, to view and discuss the device. CAS and Center for Injury Research (CFIR) also submitted additional test data to the agency using the JRS.

We note that the agency is also aware of tests used by manufacturers to assess a vehicle's rollover performance during vehicle development and conditions they are designed to represent such as the curb trip, soil trip, the bounce over, etc.

Viano D., Parenteau C., “Rollover Crash Sensing and Safety Overview,” SAE International, 2004-01-0342.

As noted earlier in this document, rollover crashes are complex and chaotic events. Rollovers can range from a single quarter turn to eight or more quarter turns, with the duration of the rollover crash lasting from one to several seconds. The wide range of rollover conditions occurs because these crashes largely occur off road where the vehicle motion is highly influenced by roadside conditions.

The variety and complexity of real-world rollover crashes create significant challenges in developing dynamic tests suitable for a Federal motor vehicle safety standard. Rollover crash tests can have an undesirable amount of variability in vehicle and occupant kinematics.

In assessing whether a potential dynamic test would be appropriate for a Federal motor vehicle safety standard, the agency must consider such issues as (1) whether the test is representative of real-world crashes with respect what happens to the vehicle and any specified test dummies; (2) for the specific aspect of performance at issue, whether the test is sufficiently representative of enough relevant real-world crashes to drive appropriate countermeasures and, if not, the number and nature of necessary tests to achieve that purpose; (3) whether the test is repeatable and reproducible so that the standard will be objective; and (4) whether the test dummies to be specified are biofidelic for the purposes used.

We have reviewed the comments recommending a dynamic test and are including our analysis of those comments in an appendix to this document. NHTSA appreciates the information and data that have been provided on this subject. We decline, however, to pursue a dynamic test as part of this rulemaking, or to initiate at this time a separate rulemaking for a dynamic test.

As noted above, we explained in the NPRM that we were unaware of any dynamic test procedure that provides a sufficiently repeatable test environment. After reviewing the public comments and for reasons discussed in the appendix, we continue to take that position. While some commenters argued that certain procedures are repeatable, the agency was not persuaded by the arguments and data they presented. Moreover, for reasons discussed in the appendix, there are significant issues associated with each of the cited dynamic test procedures related to possible use in a Federal motor vehicle safety standard.

Also of importance for this rulemaking, even if NHTSA were to identify a particular dynamic test procedure, among the many known to be available, as likely to be suitable for assessing roof crush resistance (something we have not been able to do thus far), we would need additional years of research to evaluate and refine, as necessary, the procedure to develop a proposal, including evaluating it in the context of the current vehicle fleet. It is also not known whether any dynamic test requirement that might be identified by NHTSA's research would produce significant additional benefits beyond those that will be produced by the substantial upgrade of the quasi-static procedure that we are adopting in this rule.

NHTSA agrees, however, with pursuing a dynamic test as our ultimate goal. We would like to have one for rollover crashes just as we do for front and side crashes. Unfortunately, we cannot adopt or even propose one now because of issues related to test repeatability, a dummy, and lack of injury criteria. We are pursuing further research for a dynamic test, but we expect that it will take a number of years to resolve these issues. In the meantime, we do not want to delay a significant upgrade of FMVSS No. 216 that will save 135 lives each year.

2. Vehicle Application

FMVSS No. 216 currently applies to passenger cars, and to multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less. In our August 2005 NPRM, in addition to proposing upgraded performance requirements, we proposed to extend the application of the standard to vehicles with a GVWR of up to 4,536 kilograms (10,000 pounds). We proposed to permit vehicles manufactured in two or more stages, other than chassis-cabs, to be certified to the roof crush requirements of FMVSS No. 220, instead of FMVSS No. 216. We stated that we believed that the requirements of FMVSS No. 220 appeared to offer a reasonable avenue to balance the desire to respond to the needs of multi-stage manufacturers and the need to increase safety in rollover crashes.

The commenters generally supported extending the application of FMVSS No. 216 to vehicles with a GVWR of up to 4,536 kilograms (10,000 pounds). The National Transportation Safety Board (NTSB) stated that heavier vehicles such as 12- and 15-passenger vans, not currently subjected to the standard, are experiencing patterns of roof intrusion greater than vehicles already subject to the requirements. That commenter also cited two investigations it conducted concerning the safety need for vehicles between 6,000 and 10,000 pounds GVWR to meet roof crush resistance requirements.

We received a number of comments concerning requirements for multi-stage vehicles and vehicles with altered roofs, including ones from Advocates, the National Truck Equipment Association (NTEA), the Recreation Vehicle Industry Association (RVIA) and the National Mobility Equipment Dealers Association (NMEDA). The concerns and recommendations of these commenters varied considerably. We discuss and address the comments later in this document. For purposes of this more general section concerning applicability, we note that we are providing a FMVSS No. 220 option for some but not all multi-stage vehicles and for vehicles which are altered in certain ways to raise the height of the roof. We also note that, for reasons discussed in that section, we are excluding a narrow

category of multi-stage trucks from FMVSS No. 216 altogether.

Subject to the limited exceptions/alternatives/exclusions noted in the previous paragraph or already included in FMVSS No. 216, and for the reasons discussed in the NPRM and in this document, we are extending the application of the standard to vehicles with a GVWR of up to 4,536 kilograms (10,000 pounds).

This final rule will address the NTSB's recommendation H-03-16, to include 12- and 15-passenger vans in FMVSS No. 216, to minimize the extent to which survivable space is compromised in the event of a rollover accident.

3. Single-Sided or Two-Sided Tests

Under the current version of FMVSS No. 216, vehicles must meet the standard's requirements for both the driver and passenger sides of the vehicle. Thus, roof crush resistance protection is required for both the driver and passenger sides of the vehicle. The standard specifies a single-sided test. While a vehicle must meet the standard's test requirements, regardless of whether it is tested on the driver or passenger side, a particular vehicle is tested on only one side.

As discussed in the NPRM, a number of commenters on our 2001 RFC suggested that the agency specify a two-sided test requirement, i.e., a requirement that each vehicle must meet the standard's test requirements when tested sequentially, first on one side of the vehicle, and then on the other side. Commenters making this recommendation included Public Citizen and CFIR. The commenters stated that vehicle occupants on the far side of the rollover have a much greater risk of serious injury than occupants on the near side,

and argued that a two-sided requirement is needed to protect far side occupants.

Near side is the side toward which the vehicle begins to roll and the far side is the trailing side of the roll.

In the NPRM, the agency summarized the results of six two-sided tests it had conducted in light of those comments. The testing sought to evaluate the strength of the second side of the roof of vehicles whose first side had already been tested. In this testing, after the force was applied to one side of the roof over the front seat area of a vehicle, the vehicle was repositioned and force was then applied on the opposite side of the roof over the front seat area. In performing these tests on both sides of a vehicle, the agency used the platen angle currently specified in FMVSS No. 216 (5 degree pitch forward and 25 degree rotation outward, along its lateral axis). We concluded that the strength of the roof on the second side of some vehicles may have been increased or decreased as a result of the deformation of the first side of the roof. The agency indicated that it planned to conduct further research before proposing rulemaking in this area.

In commenting on the NPRM, a number of consumer advocacy organizations and other commenters strongly supported a two-sided test requirement. These commenters included, among others, Public Citizen, CFIR, CAS, and Advocates. Supporters of a two-sided test requirement argued that more damage occurs to the far (or trailing) side of the vehicle in a rollover crash, and a two-sided test would better reflect this real-world intrusion. They further argued that when the near side roof and windshield are compromised in a rollover, the far side will not be able to withstand the forces of the event, and, consequently, facilitate roof collapse. ARCCA, Inc., Consumers Union, and Safety Analysis and Forensic Engineering (SAFE) suggested a two-sided test would simulate the impact that occurs in the majority of rollover incidents.

In light of the substantial interest in a two-sided test requirement, NHTSA expanded the series of two-sided roof crush tests discussed in the NPRM. In our January 2008 SNPRM, we explained that we had, by that time, conducted a total of 26 sequential two-sided tests, and announced that we were releasing these data to the public in conjunction with the SNPRM.

We stated in the SNPRM that the two-sided test results showed the first side test generally produces a weakening of the structure. This was shown by the fact that the recorded SWR for the second side was generally lower than for the first side. On average, the peak strength for the second side was reduced by 8.7 percent. However, for several of the vehicles, we observed considerably higher reductions in peak strength. Of the 26 vehicles that had been tested by that time, excluding the Chevrolet Express, six experienced reductions in strength of 19 percent or greater. We excluded the Chevrolet Express because of a test anomaly.

Between the first and second side tests, the front door on the tested side was opened. Because of damage to the vehicle during the first side test, the door would not properly close. The door was clamped until the latch engaged, locking the door in place. This may have compromised the structural integrity of the roof and reduced the measured peak load on the second side.

With respect to two-sided vehicle testing, we stated that we believed that the post-NPRM tests provided the agency with sufficient additional information for the agency to consider a two-sided test requirement for the final rule. We stated that we would evaluate both the single-sided and two-sided testing alternatives for the final rule, and requested comments to help us reach a decision on that issue.

Comments

In commenting on the SNPRM, a number of consumer advocacy organizations continued to strongly support a two-sided test requirement. Public Citizen stated that in a vast majority of rollover cases, the injured party was typically seated on the far side, that is, the side of the second impact. It argued that it is not possible to upgrade FMVSS No. 216 without a two-sided test requirement. Some commenters argued, as they had in commenting on the NPRM, that they believe SAFETEA-LU requires a two-sided test.

The Alliance stated that it believes the agency has provided insufficient justification for two-sided testing. It stated that the agency has not provided analysis demonstrating that two-sided testing relates to real-world safety.

The Alliance also expressed concern that two-sided testing would amplify variability and repeatability problems. That organization argued that the agency's limited repeatability testing for a potential two-sided requirement indicates poor repeatability in SWR between the first and second side tests for the same vehicle. The Alliance cited agency tests of the Lincoln LS and Buick LaCrosse.

According to the Alliance, these differences may be due solely to lack of test procedure repeatability and test lab reproducibility, rather than any real weakening or strengthening of the roof structure due to the first side test. That commenter stated that in a two-sided scenario, the deformed shape of a vehicle tested for roof strength on one side between any two tests is not identical. The starting point for the roof-strength testing on the second side is therefore, according to the Alliance, inherently different and results in substantial variability in measured roof strength.

AIAM stated that based on the information and analysis provided by

the agency regarding the two-sided test, it believes that the test shows enough potential to merit further consideration by the agency. AIAM argued that additional analysis would be needed before it could provide a preferred regulatory approach, but indicated that the two-sided approach would more directly address the multiple roof contact weakening phenomenon.

Agency Response

After carefully considering the comments and available information, we have decided, for the reasons discussed below, to adopt a two-sided test requirement.

In responding to the comments, we begin by addressing the argument raised by some commenters that SAFETEA-LU requires a two-sided test. Public Citizen stated that the agency has “ignored the express requirement of a two-sided test.” That organization cited the statutory language requiring NHTSA to upgrade FMVSS No. 216 related to roof strength “for driver

and

passenger

sides.”

(Emphasis added by Public Citizen.)

As discussed earlier in this document, under the current version of FMVSS No. 216, vehicles must meet the standard's requirements for both the driver and passenger sides of the vehicle, i.e., a vehicle must meet the standard's test requirements regardless of whether it is tested on the driver or passenger side. Thus, while the standard specifies a single-sided test, roof crush resistance protection is required for both the driver and passenger sides of the vehicle. Similarly, upgrading the current performance requirements so that vehicles must provide protection at a significantly higher SWR under a single-sided test procedure would result in upgraded protection for both the driver and passenger sides. Thus, while we understand the safety arguments raised by Public Citizen and other commenters favoring a two-sided test, we believe that the language in SAFETEA-LU does not mandate a two-sided test requirement, only that upgraded protection be provided for both the driver and passenger sides.

We also note that the issue of whether to adopt a two-sided test is related to the decision of what stringency to adopt. For any baseline single-sided test requirement at a particular SWR, either increasing the SWR for the single-sided test or adding a two-sided test requirement at the same SWR would represent an increase in stringency. Therefore, in reaching a decision on these issues, we have considered them together.

To help evaluate the merits of a two-sided test requirement, the agency analyzed 1997 through 2006 NASS-CDS rollover crash data, involving restrained occupants.

Only vehicles that overturned and experienced 2 or more quarter turns were included. This study included 4,030 NASS-CDS investigated vehicles, and excluded convertibles and vehicles that had a concentrated loading due to a collision between a fixed object (pole or tree) and the roof.

See

report

Evaluation of 2 Side Roof Crush Testing

placed in the docket with this notice.

The data were analyzed for differences in injury risk for the near and far side occupants and also to ascertain any disparity in the amount of roof intrusion. For all rollovers involving two or more quarter turns, the data showed that there are a similar number of near and far side occupants involved in the event. A further review of the injury outcomes showed that the injuries to far side occupants occur at a slightly higher frequency than injuries to near side occupants.

The occupant injury data were further analyzed to determine whether the relative proportion of near and far side injured occupants varied with the amount of roof intrusion. The injury outcomes for occupants in vehicles with less than 12 cm (5 inches) of near side roof intrusion show higher frequency of injury for the far side occupant at the various injury levels. The outcomes for injured occupants in vehicles with 12 cm (5 inches) or greater near side intrusion have similar percentages of severe injuries between near and far occupants. Based on this analysis, the data indicate there may be some higher risk for far side occupants at lower levels of intrusion; however, none of the results was statistically significant.

The analysis investigated the difference in roof intrusion between the near and far side of the vehicle that experienced two quarter turns or more. For the 4,030 NASS-CDS vehicles, there was a weighted average maximum vertical intrusion of 7.9 cm (3.1 inches) on the near side and 10.9 cm (4.3 inches) on the far side of the rollover-involved vehicle. The far side of the vehicle averaged 3 cm (1.2 inches) more vertical intrusion than the near side.

The analysis also investigated the intrusion difference between the near and far side grouped by the severity of the rollover. (Severity of the rollover was defined by single or multiple roof-to-ground contacts). The data showed a 3 cm (1.2 inch) bias toward the far side intrusion, independent of the severity of the rollover. For example, vehicles experiencing five or more quarter turns had 9.2 cm (3.6 inches) of near-side intrusion compared to 12.2 cm (4.8 inches) of far-side intrusion. The analysis concluded for crashes with multiple roof-to-ground contacts (or severe rollovers), there is a statistically insignificant bias on the far side.

Since the publication of the SNPRM, the agency has conducted an additional five tests

as part of its evaluation, for a total of 31 two-sided tests.

The test results for all 31 two-sided tests are summarized in Appendix B of this document.

The test reports for the additional vehicle tests conducted by NHTSA are being made available to the public through the agency's internet vehicle crash test database. We are placing a memorandum in the docket which provides the Web address for that database and lists the vehicle models and test numbers that are needed to reference the information in the database. The agency incorporates by reference these test reports as part of the record for this rulemaking.

We note that we also conducted a test of a Smart ForTwo. However, we did not include these test results as part of our evaluation because the vehicle is not typical of a significant number of vehicles in the fleet.

On average, the peak strength for the second side was reduced by 8.4 percent. This reduction in strength is consistent with our NASS-CDS analysis, showing a slight increase of intrusion on the second side. This also may explain the increased risk to injury for far side occupants. In all the tests, the windshield fractured during the first side test and there was not a catastrophic collapse of the roof on the second side.

In general, there was a good correlation in peak strength between the first and second side. The agency did test four vehicles that resulted in increased strength on the second side. However, for several of the vehicles, we observed considerably higher reductions in peak strength. Of the 31 vehicles tested, again excluding the Chevrolet Express, seven experienced reductions in strength of 19 percent or greater. The two-sided testing conducted by NHTSA indicated an average difference of approximately 7.1 percent lower peak force for the second side in vehicles under 2,722 kilograms (6,000 pounds) GVWR and 14.9 percent lower peak force for the second side in vehicles over 2,722 kilograms (6,000 pounds) GVWR.

We have decided to adopt a two-sided test in light of several considerations. First, we believe a two-sided test is more representative of the higher severity rollover crashes in which a vehicle experiences multiple quarter turns. In such crashes, the vehicles sometimes experiences a significant impact on one side of the vehicle and,

as the vehicle continues to turn, another significant impact on the other side of the vehicle. A two-sided test will help ensure that the impact on the first side of the vehicle does not cause excess damage that will prevent the vehicle from providing protection during the impact on the second side of the vehicle.

Moreover, as discussed in the FRIA, the greater stringency associated with a two-sided test requirement will provide greater benefits.

While we recognize that a two-sided test requirement affects the stringency of the standard, as compared to a single-sided test requirement at the same SWR, we believe that it does not raise concerns related to test procedure repeatability and test lab reproducibility.

In addressing this issue, we note that the test conducted on the second side is identical to the test conducted on the first side. Thus, the second side test by itself is repeatable and reproducible, for the same reasons the first side test is repeatable and reproducible.

As noted by the Alliance, the “starting point” for the second side test is different than for the first side test in that the vehicle may have experienced damage during the first side test. However, it is the purpose of a two-sided test requirement to limit such damage, to the extent such damage would prevent compliance with the standard's performance requirements during the second side test.

As to the Lincoln LS and Buick Lacrosse repeat tests cited by the Alliance, the change in peak SWR between the first and second side test was −21.3 percent and −8.7 percent for the two Lincoln LS vehicles tested, and −13.5 percent and −3.4 percent for the two Buick Lacrosse vehicles tested. For the Lincoln LS, there was good correlation between the load-deformation curves on the first side in the two tests. However, on the second side, the load-deformation curves diverge prior to the peak SWR. Further, in one Lincoln LS test, the second side correlated well with the first side. The other test did not show the same correlation on the second side, which led us to believe internal structural damage to the roof during the first side test was the cause. With respect to the Buick Lacrosse, the agency identified a pre-test windshield crack as the likely reason for the difference in outcome between the two tests. The load-deformation curves for the first side did not reach the same peak load; however, there is good correlation on the second side. Thus, we believe the differences relate to vehicle performance instead of test procedure issues.

It is important to note that the Lincoln LS and Buick Lacrosse vehicles were not subject to an FMVSS incorporating a two-sided requirement or an SWR requirement above 1.5, so they were not designed to meet such a requirement (two-sided test requirement at the tested SWR). Manufacturers can ensure that a vehicle meets a two-sided test requirement by designing it so that they will be able to meet the second-side test despite whatever damage may occur in the first side test. As a general matter, the greater the structural damage that occurs in the first-side test, the greater the variability one would expect in the second-side test. We note that the performance requirement is not expressed in terms of the percentage difference in damage between the first-side test and the second test; instead, the vehicle must meet the same specified performance criteria in both tests. We also note that the first-side test is conducted only up to the SWR specified in the standard.

Finally, we note that issues raised by commenters concerning varying platen angle and size for the second-side test are addressed later in this document in the section addressing aspects of the test procedure.

4. Upgraded Force Requirement—Specified Strength to Weight Ratio (SWR)

As discussed earlier, FMVSS No. 216 currently requires that the lower surface of the test platen not move more than 127 mm (5 inches), when it is used to apply a force equal to 1.5 times the unloaded vehicle weight to the roof over the front seat area. In the NPRM, the agency proposed to require that the roof over the front seat area withstand a force increase equal to 2.5 times the unloaded weight of the vehicle, and to eliminate the 22,240 Newton (5,000 pound) force limit for passenger cars.

NHTSA explained that it believes that FMVSS No. 216 could protect front seat occupants better if the applied force requirement reduced the extent of roof crush occurring in real world crashes. That is, the increased applied force requirement would lead to stronger roofs and reduce the roof crush severity observed in real world crashes. We observed that in many real-world rollovers, vehicles subject to the requirements of FMVSS No. 216 experienced vertical roof intrusion greater than the test plate movement limit of 127 mm (5 inches).

In explaining the proposed 2.5 value for SWR, the agency noted that it previously conducted a study

(Rains study) that measured peak forces generated during quasi-static testing under FMVSS No. 216 and under Society of Automotive Engineers (SAE) J996 inverted drop testing. In the Rains study, nine quasi-static tests were first conducted. The energy absorption was measured and used to determine the appropriate corresponding height for the inverted drop conditions. Six of the vehicles were then dropped onto a load plate. The roof displacement was measured using a string potentiometer connected between the A-pillar and roof attachment and the vehicle floor. The peak force from the drop tests was limited to only the first 74 mm (3 inches) of roof crush because some of the vehicles rolled and contacted the ground with the front of the hood. Similarly, the peak quasi-static force was limited during the first 127 mm (5 inches) of plate movement.

Glen C. Rains and Mike Van Voorhis, “Quasi Static and Dynamic Roof Crush Testing,” DOT HS 808-873, 1998.

This report showed that for the nine quasi-static tests, the peak force-to-weight ratio ranged from 1.8 to 2.5. Six of these vehicle models were dropped at a height calculated to set the potential energy of the suspended vehicle equal to the static tests. For these dynamic tests, the peak force-to-weight ratio ranged from 2.1 to 3.1. In sum, the agency tentatively concluded that 2.5 was a good representation of the observed range of peak force-to-weight ratio.

As to eliminating the 22,240 Newton force limit for passenger cars, the agency noted that the limit was included when the standard was first issued. The effect of the limit was that passenger cars weighing more than 1,512 kilograms (3,333 pounds) were subjected to less stringent requirements. The purpose of the limit was to avoid making it necessary for manufacturers to redesign large cars that could not meet the full roof strength requirements of the standard.

At the time, the agency believed that requiring larger passenger cars to comply with the full (1.5 times the unloaded vehicle weight) requirement would be unnecessary because heavy passenger cars had lower rollover propensity. However, as discussed in the NPRM, the agency tentatively concluded that occupants of passenger cars weighing more than 1,512 kilograms (3,333 pounds) are sustaining rollover-related injuries and that those cars should be able to comply with the proposed requirements.

See

54 FR 46276.

The agency stated in the NPRM that it believed that manufacturers would comply with the upgraded standard by strengthening reinforcements in roof pillars, by increasing the gauge of steel used in roofs or by using higher strength materials.

In the SNPRM, we noted that we had been carefully analyzing the numerous comments received in response to the proposal, and the various additional vehicle tests conducted after publication of the NPRM. We invited comments on how the agency should factor in this new information into its decision. We stated that while the NPRM focused on a specified force equivalent to 2.5 times the unloaded vehicle weight, the agency could adopt a higher or lower value for the final rule.

In the SNPRM, we observed from the recent vehicle testing (focusing on the single-sided test results) that the range of SWRs for vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less tended to be higher than the range of SWRs for vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds). The SWR of many late model vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less was substantially higher than the 2.5 value the agency focused on in the NPRM. Conversely, only two vehicles we tested with a GVWR greater than 2,722 kilograms (6,000 pounds) exceeded the 2.5 value.

We noted in the SNPRM that the PRIA had examined the proposed SWR of 2.5 and the alternative SWR of 3.0 times the unloaded vehicle weight. The agency included in the SNPRM discussion and analysis concerning a number of factors expected to change the estimated impacts, and sought comments concerning impacts of SWR levels of 2.5, 3.0 and 3.5.

Comments on the NPRM

In general, vehicle manufacturers supported an SWR of 2.5, while safety advocacy groups recommended a more stringent standard with the majority supporting a 3.5 SWR requirement.

Vehicle manufacturers, including General Motors Corporation (GM), Ford Motor Company (Ford), DaimlerChrysler Corporation,

Porsche Cars North America (Porsche), Toyota Motor North America (Toyota), and Nissan North America (Nissan), and the Alliance supported the proposed 2.5 SWR level, with caveats about sufficient leadtime and other requested changes to the test procedure, but expressed concern about raising the SWR further. The Alliance cautioned against increasing the SWR beyond 2.5 due to the potential adverse effects of increased mass. It stated that recommendations in the docket for higher levels did not attempt to account for the potential effect on the static stability factor (SSF) of adding structure necessary to comply with higher standards.

In August 2007, Daimler and Chrysler separated. All comments submitted to the agency prior to that date will be noted in this document as DaimlerChrysler. Mercedes-Benz USA and Chrysler LLC submitted comments separately afterwards and will be referenced accordingly.

Commenters supporting a 3.5 SWR included Lipsig, Shapey, Manus & Moverman (LSMM), Consumers Union, Center for the Study of Responsive Law (CSRL), Mr. Sances, Perrone Forensic Consulting (Perrone), Ms. Lawlor, Mr. Clough, Xprts, Mr. Nash, Mr. Friedman, and Forensic Engineering (FEI). Consumers Union, LSMM, Ms. Lawlor, Mr. Clough, and Mr. Sances supported a 3.5 SWR based on, among other things, the performance of the Volvo XC90. Commenters stated that the Volvo XC90 has heightened roof strength resistance through light-weight materials making it possible to avoid any unnecessary increases in vehicle weight which could adversely affect rollover propensity. In supporting more stringent roof crush resistance requirements, the CSRL stated that NHTSA should consider using its technology-forcing authority.

Several commenters supported an SWR of 4.0 or higher. These commenters included Mr. Slavik, ARCCA, Technical Services, and FEI. The commenters suggested that higher strength steel alloy, changes to the cross sectional thickness of roof components, and other design changes would make increasing the SWR feasible and cost effective.

In connection with arguments that the agency should base the level of the standard on the performance of the Volvo XC90, Ford commented that in considering the stringency of an SWR requirement, roof SWR does not discriminate vehicles by roof strength. It noted that the roof strength required to achieve a specific SWR depends on the vehicle's unloaded vehicle weight (UVW). Ford stated that two vehicles with the same SWR, but different UVWs, may have roof strength levels that are actually several thousand pounds apart. That company argued that the agency's 2.5 SWR proposal is very stringent. Ford stated that vehicle roof designs are essentially the same for all passenger carrying vehicles, and that A pillars are A pillars and B pillars are B pillars, regardless of vehicle type, i.e., the constraints on a roof system design are applicable to all affected vehicles. That company argued that because a particular vehicle can achieve a roof SWR of 3.5, because it has a lower UVW as compared to a full size pickup, does not mean that 3.5 should be the regulatory requirement.

Comments on the SNPRM

In commenting on the SNPRM, vehicle manufacturers continued to support an SWR of 2.5, with safety advocacy groups recommending a more stringent requirement.

The Alliance recommended that all vehicles should be held to the same requirements and that a separate requirement should not be afforded for heavy vehicles. Mercedes-Benz suggested that, for a two-sided test requirement, the SWR on the second side should be lower than what would be required for the first side. This would reflect the lower force levels in a rollover that it said the second side would experience.

IIHS supported raising the SWR to 3.0 or higher in a one-sided test. IIHS stated that its new analysis justifies such a requirement.

Agency Decision and Response

After carefully considering the comments and available information, and for the reasons discussed below, we have decided to adopt an SWR requirement of 3.0 for vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less, and 1.5 for vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds).

While this rulemaking involves a number of key decisions, the selection of an SWR requirement is the most important one for both costs and benefits. Our analysis, presented in detail in the FRIA, shows that for the alternatives we evaluated, benefits in terms of reduced fatalities continue to rise with higher SWR levels due to reduced intrusion. The benefits continue to rise because, for vehicles designed to have higher SWR levels, the vehicle roofs experience less intrusion in higher severity crashes. However, costs also increase substantially with higher SWR levels, so NHTSA must select the appropriate balance of safety benefits to added costs.

Under the Safety Act, NHTSA must issue safety standards that are both practicable and meet the need for motor vehicle safety. 49 U.S.C. 30111(a). The agency considers economic factors, including costs, as part of ensuring that standards are reasonable, practicable, and appropriate.

Motor Vehicle Manufacturers Association

State Farm

, 463 U.S. 29, 54-55 (1983), the Supreme Court indicated that the agency must, in making decisions about safety

standards, consider reasonableness of monetary and other costs associated with the standard. It stated, however, that “(i)n reaching its judgment, NHTSA should bear in mind that Congress intended safety to be the preeminent factor under the Motor Vehicle Safety Act:”

The Committee intends that safety shall be the overriding consideration in the issuance of standards under this bill. The Committee recognizes * * * that the Secretary will necessarily consider reasonableness of cost, feasibility and adequate leadtime. S. Rep. No. 1301, at 6, U.S. Code Cong. & Admin. News 1966, p. 2714.

In establishing standards the Secretary must conform to the requirement that the standard be practicable. This would require consideration of all relevant factors, including technological ability to achieve the goal of a particular standard as well as consideration of economic factors. Motor vehicle safety is the paramount purpose of this bill and each standard must be related thereto. H.Rep. No. 1776, at 16.

Thus, in making our decision concerning SWR, we are guided by the statutory language, legislative history, and the Supreme Court's construction of the Safety Act, as well as by the specific requirement in SAFETEA-LU for us to upgrade FMVSS No. 216 relating to roof strength for driver and passenger sides for motor vehicles with a GVWR of not more than 4,536 kilograms (10,000 pounds). We consider both costs and benefits, bearing in mind that Congress intended safety to be the preeminent factor under the Safety Act.

As indicated above, while benefits continue to rise with higher SWR levels, costs also increase substantially. The challenge is to push to a level where the safety benefits are still reasonable in relation to the associated costs. As part of this, we consider issues related to cost effectiveness. The agency's analysis of cost effectiveness is presented in the FRIA and summarized in this document.

Another important factor in the selection of the SWR requirements is that there are much higher costs relative to benefits associated with any level SWR requirement for vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds) as compared to the lighter vehicles currently subject to the standard.

There are a number of reasons for this differential between heaver and lighter vehicles. The absolute strength needed to meet a specific SWR is a function of the vehicle's weight. By way of example, to meet a 2.0 SWR, a vehicle that weighs 1,360 kilograms (3,000 pounds) must have a roof structure capable of withstanding 26,690 N (6,000 pounds) of force, while a vehicle that weighs 2,268 kilograms (5,000 pounds) must have a roof structure capable of withstanding 44,482 N (10,000 pounds) of force. This means more structure or reinforcement are needed for the heavier vehicle, which means more cost and weight. Moreover, vehicles in the heavier category have not previously been subject to FMVSS No. 216, so they have not been required to meet the existing 1.5 SWR single-sided requirement.

At the same time, these heavier vehicles account for only a very small part of the target population of occupants who might benefit from improved roof strength. Only 5 percent of the fatalities in the overall target population (33 in terms of a specific number) occur in vehicles over 2,722 kilograms (6,000 pounds) GVWR. Ninety-five percent of the fatalities (635 in terms of a specific number) occur in vehicles

under

2,722 kilograms (6,000 pounds) GVWR. These differences reflect the fact that there are far fewer vehicles in this category in the on-road fleet, and may also reflect the vehicles' size and weight as well as their frequency of use as working vehicles. Heavier vehicles generally are less likely to roll over than lighter vehicles.

We recognize the argument that all light vehicles should meet the same SWR requirements, to ensure the same minimum level of protection in a rollover crash. However, in selecting particular requirements for a final rule, we believe that our focus must be on saving lives while also considering costs and relative risk. What is necessary to meet the need for safety and is practicable for one type or size of vehicle may not be necessary or reasonable, practicable and appropriate for another type or size of vehicle. Thus, to the extent the goal of establishing the same SWR requirements for all light vehicles would have the effect of either unnecessarily reducing the number of lives saved in lighter vehicles or imposing substantially higher, unreasonable costs on heavier vehicles despite their lesser relative risk, we believe it is appropriate to adopt different requirements for different vehicles. We also observe that because the same SWR requirement is significantly more stringent for heavier vehicles than lighter vehicles (due to SWR being a multiple of unloaded vehicle weight), establishing the same SWR requirement for heavier vehicles is not simply a matter of expecting manufacturers to provide the same countermeasures as they do for light vehicles.

Vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less.

Our decision to adopt a 3.0 SWR requirement for vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less, i.e., the vehicles currently subject to the standard, reflects the higher life-saving benefits associated with that requirement. It also reflects our consideration of the test results of current vehicles. We believe the high SWR levels that are currently being achieved for a range of light vehicles demonstrate that manufacturers can achieve this SWR level for these vehicles.

An SWR requirement of 3.0 prevents about 66 percent more fatalities than one at 2.5, 133 instead of 80. However, costs increase by a considerably higher percentage, resulting in a less favorable cost per equivalent life saved, $5.7 million to $8.5 million for 3.0 SWR as compared to $3.8 million to $7.2 million for 2.5 SWR.

In these particular circumstances, we believe that a 3.0 SWR requirement is appropriate and the costs reasonable given the increased benefits. While the cost per equivalent life saved is relatively high compared to other NHTSA rulemakings, we conclude that the higher safety benefits, the legislative mandate for an upgrade, the technical feasibility of making roofs this strong, and the fact that these costs are generally within the range of accepted values justify moving NHTSA's roof crush standards to a 3.0 SWR for vehicles that have been subject to the 1.5 SWR requirements.

We decline, however, to adopt an even higher SWR requirement. In considering higher SWR requirements at this level, costs continue to increase at a considerably higher rate than benefits. The FRIA estimates that while a 3.5 SWR requirement for these vehicles would result in higher benefits, preventing 175 instead of 133 fatalities, total costs would increase to $1.6 billion to $2.3 billion (about $800 million to $1.1 billion above the total costs for the 3.0 SWR requirement) and the overall cost per equivalent life saved for these vehicles would increase to $8.8 to $12.3 million. A 3.5 SWR requirement would thus result in an approximate doubling of the costs beyond those of a 3.0 SWR requirement, and deliver about

1/3

more benefits.

Vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds) and less than or equal to 4,536 kilograms (10,000 pounds).

Vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds) are not currently subject to FMVSS No. 216 and, because of their greater unloaded vehicle weight, these vehicles pose greater design challenges. Moreover,

given the relatively small target population for these vehicles, the benefits will necessarily be small regardless of the SWR selected.

After considering our original proposal of a SWR of 2.5 and the available information, we have concluded that a SWR of 1.5 is appropriate for these heavier vehicles. The requirement we are adopting is more stringent than the longstanding requirement that has applied to lighter vehicles until this rulemaking because it is a two-sided requirement. The FRIA estimates that two fatalities and 46 nonfatal injuries will be prevented annually by this requirement. Because of the high cost relative to the benefits for all of the alternatives for these heavier vehicles, from the 1.5 SWR alternative and above, any alternative we select would adversely affect the overall cost effectiveness of this rulemaking (covering all light vehicles).

We believe that a SWR of 1.5 is appropriate for these heavier vehicles. Given the requirements of SAFETEA-LU, we need to ensure that the standard results in improved real world roof crush resistance for these vehicles. We decline, however, to adopt a SWR higher than 1.5 for vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds), given the small additional benefits (4 additional lives saved) and substantially higher costs. Adopting a SWR of 2.0 for these vehicles would more than double the costs of this rule for these vehicles to prevent 4 additional fatalities and 137 nonfatal injuries.

Other issues related to strength requirements and SWR.

As indicated above, the Alliance cautioned against increasing the SWR beyond 2.5 for lighter vehicles due to the potential adverse effects of increased mass. It stated that recommendations in the docket for higher levels did not attempt to account for the potential effect on the SSF of adding structure necessary to comply with higher standards.

We do not believe that it is necessary to account for that effect. We note that the agency has considered a number of issues related to added weight as part of the FRIA, including possible adverse effects to safety. Based on our analysis, we believe that today's rule will not result in adverse effects to safety as a result of added weight.

For a number of reasons, including ones related to CAFE standards, fuel prices, and rollover propensity, we believe manufacturers will strive to minimize the weight impacts of added roof strength. While there is a great deal of uncertainty regarding the actual changes that manufacturers will initiate in response to this rule, there are numerous ways to address both roof strength and rollover propensity simultaneously. This final rule provides substantial leadtime within which to choose among those ways and make design changes that avoid adversely affecting that propensity. There is evidence from current NCAP ratings that manufacturers are routinely doing so. Manufacturers generally strive to maintain or improve their NCAP ratings to help market their vehicles. The agency believes that this concern over NCAP ratings would preclude a design strategy that unnecessarily increases CG and degrades SSF. Further, agency testing of 10 redesigned vehicles with higher roof strengths found that manufacturers had maintained SSF levels while increasing roof strength in newly redesigned models.

A detailed discussion of issues related to added weight and SSF is included in the FRIA, and there is also additional discussion later in this document.

Mercedes-Benz suggested that, for a two-sided test requirement, the SWR on the second side should be lower than what would be required for the first side. According to Mercedes, this would reflect the lower force levels in a rollover that it said the second side would experience. However, as discussed above in the section on single-sided or two-sided tests, the agency's analysis of NASS data indicates that vehicles experience more intrusion on the far side (second side) of the vehicle than the near side. Therefore, we decline to adopt a lower SWR requirement for the second side. We note that the agency took into account the costs and benefits of a two-sided test requirement with the SWR at the same level for both sides.

As to the issue raised by CSRL about safety standards that are technology-forcing, that commenter did not provide specific information concerning what it contemplated in this area. As part of the agency's analysis of costs and benefits, we considered the use of advanced higher strength and lighter weight materials. Our analysis assumes significantly greater implementation and use of these advanced materials.

Finally, we note that several commenters suggested that the agency use alternative approaches other than unloaded vehicle weight for purposes of calculating SWR. Recommendations included using weight of the vehicle plus two occupants, or GVWR plus two occupants. We decline to change FMVSS No. 216's existing approach of using a multiple of unloaded vehicle weight for calculating the force requirement that applies to each vehicle. Using a weight higher than unloaded vehicle weight would simply represent another means of increasing stringency and would be equivalent to a requirement for a higher SWR. However, the agency has already considered alternative higher SWR levels, as well as a two-sided test requirement, which also represent an increase in stringency. Thus, the other issues we have considered ensure an appropriate level of stringency.

5. Performance Criteria—Headroom, Platen Travel, or Both

In the NPRM, we proposed to replace the current limit on platen travel (test plate movement) during the specified quasi-static test with a requirement that the crush not exceed the available headroom. We were concerned that the platen travel limit does not provide adequate protection to front outboard occupants of vehicles with a small amount of occupant headroom. We also stated that the current requirement may impose a needless burden on vehicles with a large amount of occupant headroom.

Under our proposal, no roof component or portion of the test device could contact the head or neck of a seated Hybrid III 50th percentile adult male dummy during the specified test. We believed that this direct headroom reduction limit would ensure that motorists receive an adequate level of roof crush protection regardless of the type of vehicle in which they ride. We included a definition of the term “roof component” as part of the proposal.

We noted a concern that there may be some low roofline vehicles in which the 50th percentile Hybrid III dummy would have relatively little available headroom when positioned properly in the seat. That is, we were concerned that, in some limited circumstances, the headroom between the head of a 50th percentile male dummy and the roof liner is so small that even minimal deformation resulting from the application of the required force would lead to test failure. We requested comments on whether any additional or substitute requirements would be appropriate for low roofline vehicles.

In the NPRM, the agency estimated benefits based on post-crash headroom, the only basis for which a statistical relationship with injury reduction had been established. In our January 2008 SNPRM, we explained that with additional years of available data, a statistically significant relationship between intrusion and injury for belted occupants had been established. A

study regarding this relationship was placed in the docket.

Strashny, Alexander, “The Role of Vertical Roof Intrusion and Post-Crash Headroom in Predicting Roof Contact Injuries to the Head, Neck, or Face during FMVSS 216 Rollovers.”

We also noted in the January 2008 SNPRM that in the most recent agency testing, headroom reduction had been assessed using a head positioning fixture (HPF) in lieu of a 50th percentile adult male dummy. We stated that reports on these tests explain the procedure and type of fixture used to assess headroom reduction, and that the test reports were being made available to the public. We noted further that the agency was considering whether this fixture should be specified in the final rule.

Comments

The agency received a variety of comments on the proposed headroom reduction criterion.

One group of commenters, including safety advocacy organizations, generally supported adding a headroom reduction criterion but, in some cases, argued that a platen travel criterion is also needed. Some of these commenters also argued that these criteria should be made more stringent to protect taller occupants.

Another group of commenters, including vehicle manufacturers, urged the agency to retain the current platen travel criterion instead of adopting a headroom reduction criterion. They argued, among other things, that using the headroom reduction criterion would add unnecessary complexity to the test procedure and result in problems related to repeatability and practicability.

Specific issues raised by commenters include:

Repeatability and practicability issues.

Several commenters, including the Alliance, DaimlerChrysler, GM, Ford, and Porsche, cited concerns related to reliability and practicability of using a test dummy for purposes of the FMVSS No. 216 quasi-static test. DaimlerChrysler, Ford and GM stated that variations in test dummy placement cause variability in the distance between the dummy head and the roof side rails. In test results cited by GM, horizontal and vertical variations of an inch or more occurred in the dummy's seating position. GM stated that this variability is further complicated when vehicles with different trim and seating options (cloth or leather, manual or power adjusters) are provided using the same vehicle architecture structure. It suggested that such options add to the variability and make the proposed requirement of measuring roof crush resistance with a seated Hybrid III dummy non-repeatable and impracticable.

Porsche also expressed concern with controlling unwanted movement of the dummy with its roof crush test set-up. The Porsche roof crush test procedure rotates the vehicle by 90 degrees because their platen press applies a load parallel to the ground. The dummy is not fixed into position and, as a result, would rotate and not be properly positioned.

Complexity.

IIHS stated that relating the allowable amount of roof crush in the quasi-static test to the headroom in specific vehicles is a good concept but that, in practice, the agency's research tests have not shown that replacing the 127 mm (5 inch) platen travel criterion with the headroom requirement would be a meaningful change to the standard and may not justify the added complications to the test procedure.

Possible conflicts with FMVSS No. 201 “Occupant protection in interior impact.”

A number of commenters, including DaimlerChrysler, Ford, GM, Ferrari and Toyota commented that the proposed headroom requirement conflicts with the intent of the upper interior requirements of FMVSS No. 201,

Occupant Protection in Interior Impact

. DaimlerChrysler and GM stated that FMVSS No. 201U

countermeasures have been specifically developed to manage head impact energy and mitigate injury potential by the dissipation of the impact energy through deformation of the trim and FMVSS No. 201U countermeasures themselves. Ford stated that head impact mitigation technologies often result in the upper interior trim, particularly the roof side rail trim, being closer to the head of occupants, thereby reducing the available distance for achieving the SWR requirement prior to headform contact. It stated that these technologies are designed to reduce the likelihood of head impact injuries, and that the proposed no-contact requirement does not account for the potential benefits of these technologies in a roof deformation situation. GM further stated that NHTSA's headroom analysis does not establish a correlation between injuries and head contact with trim components.

FMVSS 201U, refers to those aspects of FMVSS No. 201 pertaining to the upper interior trim head protection requirements.

Effects on vehicle manufacturing process

GM stated that since the vehicle roof structure is designed very early in the vehicle development process, it is not possible to reliably predict the performance or movement of interior trim in a roof crush test. It stated that structural designs must be completed early in the vehicle development process to facilitate tooling lead time. According to GM, the interior trim components (included in the proposed definition of roof component) are not designed in final form until much later in the vehicle development process. Therefore, according to that commenter, the roof structure force deflection characteristics are defined (and roof crush properties established) before manufacturers can take into account the package space and deformation requirements of the interior trim.

Reduced stringency of the standard

Several commenters, including Public Citizen, IIHS, and LSMM expressed concern that the proposed head contact criteria could reduce the residual occupant headroom required after testing, be less stringent for vehicles with existing headroom greater than 127 mm (5 inches), and thereby allow more than 127 mm (5 inches) of crush. As a result, according to these commenters, the stringency would be reduced for vehicles with greater than 127 mm (5 inches) of headroom, such as many trucks and Sport Utility Vehicles (SUVs). We note that Ford commented that most of its light trucks, multipurpose passenger vehicles and vans (LTVs) have more than 127 mm (5 inches) of platen travel prior to head contact, while passenger cars generally have less.

Alternative headroom requirement approaches

A number of commenters recommended alternative approaches to the proposed headroom requirement. Biomech Incorporated (Biomech) suggested using a one gravity static inversion test (using the FMVSS No. 301 fixture) to learn where the inverted dummy head position would be. It suggested that deformation in the roof crush test should not be permitted to reach the measured position of the inverted dummy's head.

GM, DaimlerChrysler, Toyota, Ferrari and Porsche recommended that if the agency establishes a headroom reduction criterion, it consider using a headform position procedure (HPF) that essentially represents a headform secured to an adjustable vertical support that is rigidly attached to the floor pan of the tested vehicle at the seat anchorages.

A number of these commenters also suggested that the agency consider removing any roof trim components (i.e., all headliner, trim, deployable countermeasures and grab handles) prior to testing. Further, these commenters also recommended that

head contact with the roof structure itself be the only assessment criteria for compliance certification. GM recommended that manufacturers provide the headform location to NHTSA prior to a compliance test based upon the nominal design seating positions. Toyota, by contrast, recommended the agency determine the location for the 50th percentile male head position with the Head Restraint Measuring Device (HRMD)

after first determining the H-point using the SAE J826 procedure, and then position the headform in the vehicle.

HRMD means the SAE J826 three-dimensional manikin with a headform attached, representing the head position of a seated 50th percentile male, with sliding scale at the back of the head for the purpose of measuring head restraint backset.

DaimlerChrysler recommended verifying compliance by a 200 N (44 pounds) resultant contact force in the upper neck load cell of a 50th percentile adult male Hybrid III head fixture at the location specified in the NPRM. DaimlerChrysler recommended that in the event the platen does not stop quickly enough after the resultant neck force reaches 200 N (44 pounds); the head fixture should be designed to either withdraw or become compliant by using a force limiting device in order to prevent any damage to the load cell in the dummy's head. GM also recommended a similar approach and suggested the agency consider a range of loads on the headform of 100 N (22 pounds) to 400 N (88 pounds).

Advocates recommended a maximum intrusion limit of no more than 76.2 mm (3 inches) in order to protect occupants taller than the 50th percentile male. Public Citizen recommended that NHTSA require that vehicle roof structures resist more than 76.2 mm (3 inches) of roof crush, and maintain the minimum amount of headroom proposed in the NPRM in order to reduce side window breakage and prevent B-pillar deformation, which it believes can alter seat belt geometry.

ARCCA, Mr. Slavik and the Advocates also recommended the agency use a 95th percentile adult male dummy instead of the smaller 50th percentile male to increase the stringency of the standard and further limit intrusion.

Testing with HPF:

As noted above, the agency indicated in the SNPRM that it was considering whether to specify a test using a HPF in the final rule. We received a number of comments concerning this issue.

The Alliance reiterated its recommendation that NHTSA maintain the use of the 127 mm (5 inch) platen travel criterion. That organization stated that it does not support a “no head contact” criterion, whether it is determined by use of a test dummy or via the use of an HPF with an associated contact force. The Alliance stated that the platen travel requirement would yield essentially the same roof strength and avoid unnecessary test-to-test variability and testing complexity. That organization stated that if the agency adopts a head contact criterion in the final rule, it is essential that the head contact device be a headform on a stand located at a position specified by the manufacturer and not a crash test dummy or a headform located based on what it claimed would be very unreliable and unrepeatable location data estimated from a test dummy or SAE J826 manikin (OSCAR) location. The Alliance stated that possible use of a 222 N (50 pound) contact criterion has not been supported by any scientific data.

In commenting on the SNPRM, GM stated that use of the 127 mm (5 inch) platen travel criterion rather than either a dummy or head contact fixture is required to prevent unnecessary test variation and complication while maintaining a comparable level of stringency.

AIAM did not endorse the HPF approach but suggested that the fixture might be equipped to measure neck load, to exclude incidental contact with trim items.

Public Citizen stated that defining head contact with the HPF by using force-deflection criteria would result in a significant number of front seat occupants suffering head and neck injuries.

Agency Response

After carefully considering the comments, the agency has decided to adopt the proposed headroom requirement, but with a different test procedure. Instead of specifying a procedure using a seated Hybrid III adult male dummy, we are specifying use of a HPF that positions the headform at the location of a 50th percentile adult male. To help ensure objectivity and in light of concerns about incidental contact with trim, head contact is defined as occurring when a 222 N (50 pound) resultant load is measured by a load cell on the HPF. Finally, to better ensure safety, we are retaining the current 127 mm (5 inch) platen travel requirement as well as adopting a headroom requirement.

Primary Rationale:

At the time of the NPRM, the agency estimated benefits based on post-crash headroom, the only basis for which a statistical relationship with injury reduction had been established. After the NPRM, with additional years of data available, a statistically significant relationship between intrusion and injury for belted occupants was established.

NHTSA cited its new headroom and roof intrusion analysis

in the SNPRM. The agency added two years of NASS-CDS data to each analysis and found a new, stronger negative correlation between post-crash headroom and maximum injury severity of head, neck or face from roof contact. Also, for the first time, the agency was able to find a statistically significant correlation between vertical roof intrusion and head, neck, or face injury from roof contact. Based upon this new analysis, we believe that maintaining headroom, as well as restricting the amount of intrusion (retaining the platen travel requirement) will yield benefits in rollover crashes. Therefore, we believe both criteria should be included in the final rule.

ibid

Commenters opposing adoption of a headroom requirement raised a number of concerns, including ones related to the test procedure, practicability concerns, and whether a headroom requirement would result in benefits beyond those of the platen travel requirement. The issues related to the test procedure and practicability concerns are addressed below.

As to the issue of additional benefits associated with the headroom criterion, we note that, based on our testing, in the vast majority of vehicles it is likely that the limit on platen travel will be encountered before the one on headroom reduction. For these vehicles, the new requirement will not pose any significant challenges for manufacturers, particularly in light of the changes we are making in the test procedure. However, as we also consider vehicles with less headroom and potential future vehicles, we believe there is a need to adopt a headroom reduction requirement to help ensure post-crash survival space.

In the NPRM, we raised a concern that for vehicles with greater than 127 mm (5 inches) of headroom, limiting platen travel to 127 mm (5 inches) may impose a needless burden on these vehicles. However, manufacturers generally supported retaining the platen travel limit, suggesting that the requirement is not burdensome. Moreover, as indicated above, we now have a new analysis showing a statistically significant relationship between intrusion and injury for belted occupants.

Basic Test Procedure for Measuring Head Contact:

To help analyze comments raising repeatability concerns

with the Hybrid III dummy and identifying when head contact occurred, the agency conducted a series of tests using alternative approaches. In the first series of tests conducted at NHTSA's Vehicle Research and Test Center (VRTC), the agency used a head positioning fixture developed by GM (GM-HPF).

The GM-HPF is a headform secured to an adjustable vertical support that is rigidly attached to the floor pan at the seat anchorages. The GM-HPF rigidly holds a headform in the location of a normally-seated 50th percentile male head and measures the load on the headform from contact with the interior roof as it is crushed.

See

Docket Number NHTSA-2005-22143-195

The headform consists of a skull, headskin, and 6-axis upper neck load cell from a 50th percentile male Hybrid-III dummy (Part 572, subpart E). This assembly is mounted to the end of a channeled square tube (upper post). A second, similar tube (lower post) is perpendicularly mounted to a rectangular aluminum mounting plate. The upper and lower posts attach to each other and are parallel. The upper post can slide along the lower post. This provides vertical adjustment of the headform once the fixture is mounted in the vehicle. The GM-HPF also includes four metal support straps that attach between the upper/lower post and the mounting plate, in a pyramid configuration. These straps provide rigidity to the fixture and are attached after final positioning of the headform.

In the testing conducted at VRTC,

the head position of a normally seated 50th percentile male Hybrid-III dummy was determined by placing the seat at the mid-track position and using the SAE J826 (OSCAR) device to locate the H-point. A 50th percentile male Hybrid-III dummy was then positioned per the FMVSS No. 208 seating procedure and the head location was documented using a 3-dimensional measurement device. The dummy and seat were then removed. The GM-HPF mounting plate was attached to the vehicle floor and the headform was then raised until its vertical position matched that determined from dummy placement.

See

docket entry NHTSA 2008-0015-003 for the vehicles tested with the GM-HPF.

After gaining experience with the GM-HPF, the agency developed its own, simpler HPF approach for evaluating post crash headroom. In doing so, the agency determined that it is not necessary to use a test device with the complexity of a headform based on the Hybrid III dummy head, given the nature of the performance criterion being measured. Earlier testing had shown that the skin on the Hybrid III dummy's head added a level of testing complexity that was unnecessary to the goal of identifying when roof contact occurs at a point in space. Therefore, the agency developed a simpler HPF using an FMVSS No. 201 headform that is currently used for testing instrument panels and seat backs. (This headform is effectively a 16.5 cm (6.5 inch) diameter metallic hemisphere).

During roof crush test series conducted at General Testing Laboratories,

the HPF was developed by mounting the FMVSS No. 201 headform to a cantilevered levering arm which was then attached to a tri-pod. The levering arm was maintained in position by air pressure and designed to collapse after a 222 N (50 pound) load was applied. The purpose of the cantilever design was to allow some downward movement so as not to damage the device after head contact is reached. The HPF was positioned in the vehicle at the 50th percentile male head position using the FMVSS No. 214 seating procedure recently adopted (72 FR 51908) and modified to use the OSCAR with a Head Restraint Measuring Device attached for repeatable placement. The HPF tri-pod apparatus was then rigidly secured to the floor of the vehicle. The FMVSS No. 201 headform was mounted on a 3-axis dummy neck load cell, and all loads and moments were recorded. The roof was then crushed until the unmodified interior roof made contact with the HPF and the resultant load, as measured by the load cell, exceeded 222 N (50 pounds). During our evaluation we defined “head contact” as occurring when a 222 N (50 pound) load is applied to the sphere, in the belief that this load level would correspond to structural roof contact rather than interior trim components coming loose. This was consistent with comments from DaimlerChrysler and GM that used a force load approach as a reliable method of identifying head contact and removing the uncertainty of random interior trim contact.

See

report

Two-Sided Roof Crush Testing Analysis

placed in the docket with this notice.

Our test experience with the simpler HPF proved to be repeatable in the tests and easier than using the Hybrid III dummy itself during the test.

We believe specification of the HPF appropriately addresses commenters' concerns regarding variability with regard to locating the dummy's head. With the HPF rigidly fixed to the vehicle, we also believe this addresses the concerns of manufacturers, such as Porsche, which alter the attitude of the vehicle with respect to the load press when conducting roof crush tests.

Because head contact is defined as a load on the headform, the test result is more objective/repeatable, and not sensitive to incidental contact with interior surfaces that may disengage during testing.

We disagree with comments from manufacturers that recommended the removal of the roof's interior trim prior to testing in order to simplify the procedure. The agency's headroom analysis established a correlation between injuries and head contact with a NASS-CDS roof component when the injury source was the A-Pillar, B-Pillar, front or rear header, roof rail or the roof itself. These interior surfaces are considered interior trim. We believe they should be factored in when considering the available headroom in the test. By defining head contact as occurring when a 222 N (50 pound) load is applied to the headform, we are addressing concerns about incidental contact with trim. This definition of head contact also addresses concerns about possible conflicts with the intent of FMVSS No. 201U, with respect to concerns with incidental contact. If the headform experiences a 222 N (50 pound) load, the contact is not incidental and there is a safety issue related to available headroom.

We also disagree with comments from manufacturers recommending that the head contact device be a headform on a stand located at a position specified by the manufacturer and not a crash test dummy or a headform located based on SAE J826 manikin (OSCAR) location. The HPF test procedure (as would a test procedure using a test dummy) measures head contact in the vehicle being tested. However, the approach of using a headform on a stand located at a position specified by the manufacturer would not necessarily represent the actual vehicle build.

We note that the SAE J826 mannequin has long been incorporated in NHTSA's safety standards for purposes of determining the H-point location. Issues concerning the accuracy of measurements using this device and the HRMD were addressed at length in our rulemaking upgrading our head restraints standard. Manufacturers can address concerns about different trim and seating options by factoring in the location where the headform (and also the head of a typical average size male occupant) will be under those different options.

Definition of head contact:

As noted above, the Alliance stated that possible use of a 222 N (50 pound) contact criterion has not been supported

by any scientific data. Public Citizen expressed concern that defining head contact with the HPF by means of force-deflection criteria would result in a significant number of front seat occupants suffering head and neck injuries.

We note that the load as defined is not intended to be an injury criterion, for which one would expect supporting scientific data, but is instead simply an objective way of defining head contact and avoiding treating incidental contact with loose trim as head contact. Our testing has shown, on average, once physical contact between the interior roof trim and the headform occurred resulting in the onset of a load on the headform, the platen traveled 6 mm (0.24 inches) prior to the load reaching 220 N (50 pounds). Therefore, we do not expect increased head and neck injuries from this approach. Moreover, retention of the current platen travel requirement will also prevent such increased injuries. We selected the 222 N (50 pound) contact criterion based on comments from GM and DaimlerChrysler and our own testing experience.

Possible Reduced Stringency:

IIHS, LSMM and Public Citizen expressed concern that if the platen travel requirement were not retained in addition to adopting the headroom criterion, adoption of the proposed headroom criterion would represent a decrease in stringency for the standard's performance criterion. This is not an issue since we are retaining the platen travel requirement.

Possible more restrictive requirements.

We disagree with commenters which recommended that the agency reduce the platen travel requirement to 76.3 mm (3 inches).

On average, the vehicles the agency has tested have reached the maximum SWR in 90 mm (3.5 inches) of platen travel. A requirement for reduced platen travel would represent an increase in stringency and, in many respects, would be similar to a requirement for a higher SWR. We note that the agency has already been considering the possibility of a higher SWR, as well as two-sided test requirement, which would also increase stringency. We have not conducted testing to analyze the appropriateness of applying a 3 inch platen travel requirement to all vehicles. However, we believe the other issues we have considered ensure an appropriate level of stringency.

We also do not agree with commenters recommending the use of the 95th percentile dummy (or equivalent HPF) for measuring head contact. Restricting headroom to a 95th percentile occupant is similar to limiting the platen displacement to 76.3 mm (3 inches) in increasing stringency. As indicated above, we believe the other issues we have considered ensure an appropriate level of stringency. Moreover, we believe that the relationship between vehicle headroom and occupant size is insignificant in most cases. It is likely that taller front seat occupants adjust the seat positions to prevent uncomfortable proximity to the roof such as by lowering the seat cushion bottom, increasing the seat back angle and/or adjusting the seat position further rearward.

Low roofline vehicles:

In the NPRM, we discussed possible concerns with vehicles that have relatively little available headroom when the 50th percentile adult male dummy is positioned properly in the seat. Vehicles with these aerodynamically sloped roofs will hereafter be referred as “low roofline vehicles.” We stated that we were concerned that, in some limited circumstances, the headroom between the head of a 50th percentile male dummy and the interior headliner is so small that even minimal deformation resulting from the application of the required force would lead to test failure. NHTSA requested comments on whether any additional or substitute requirements would be appropriate for low roofline vehicles in order to make the standard practicable.

Several commenters, including DaimlerChrysler, Ford, Porsche, Mitsubishi Motors R&D of America, Inc. (Mitsubishi) and Hyundai America Technical Center, Inc. (Hyundai), provided comments on low roofline vehicles. The commenters recommended that the requirements be limited to 127 mm (5 inches) of deflection for a load of 2.5 SWR in order to minimize the negative impact on continued availability of this type of vehicle if the agency were to adopt a headroom requirement. DaimlerChrysler stated that the proposed standard was not reasonable, practicable and appropriate for these types of motor vehicles as required by the Motor Vehicle Safety Act. It further stated that the agency had not demonstrated in the NPRM or the PRIA, the feasibility of going beyond 1.5 times the UVW in roof strength without head contact for vehicles with steeply raked windshields and reduced headroom.

DaimlerChrysler suggested its recommendation would be applicable to the Chrysler Crossfire, Dodge Viper, and McLaren Mercedes models and successors, which are generally designed with a steeply raked windshield and a low roofline for reduced frontal area and low drag. It further stated that this modified requirement should also apply to other kinds of vehicles, such as any two-seater that is designed with a more aggressively raked windshield. DaimlerChrysler recommended that vehicles of this type could be identified or defined based on a set of characteristics such as the Static Stability Factor (SSF) (e.g., ≥1.4), NCAP rollover rating (e.g., ≥4 stars), height-to-width ratio (e.g., ≤0.75), windshield rake angle, vehicle height, etc.

Ford stated that low roofline vehicles are not the only vehicles that have problems with limited headform clearance. It stated that vehicles that may be considered as “high roofline” can also have limited headform-to-roof clearance due to interior package design. Based on the interior package design of a particular vehicle, regardless of roof line characteristics, the critical dimension (distance between the outboard side of dummy's headform and the roof side rail trim) can be minimal. Mitsubishi commented that headform-to-roof clearance is a concern for not only low roofline vehicles but may be more generically classified as being an issue for limited headroom vehicles.

Porsche expressed concern that low roofline vehicles have less opportunity for enhanced roof structures because the focus on performance and aerodynamics virtually eliminates the option of taller pillar supports.

Hyundai stated it will be challenging for low roofline vehicles and particularly two door coupe vehicles to meet the upgraded standard because of the lack of headroom and the possibility the B-pillar may not be loaded because it is further away from the A-pillar compared to a sedan. It requested that the agency define a low roofline vehicle to explicitly include two-door coupe vehicles in the definition. It also requested that these types of vehicles be allowed to meet the current requirements until it can be demonstrated that practicability with the upgrade is feasible.

Based on its analysis, the agency believes the requirements it is adopting will not create new problems for low roofline vehicles. In our most recent two-sided research program, the agency tested a 2006 Chrysler Crossfire, a vehicle identified as a low roofline vehicle. During the first-side test, the vehicle had a peak SWR of 2.9 at 97 mm (3.85 inches) of platen displacement. Head contact based upon our criteria (222 N load on the headform) occurred at 107 mm (4.21 inches) of platen travel. This showed the maximum SWR was reached prior to head contact. On the

second side, the Crossfire reached a 2.7 SWR prior to head contact at 135 mm (5.31 inches) of platen travel.

The agency tested another low roofline vehicle, the 2007 Scion tC. This vehicle achieved a maximum SWR of 4.6 on the first side at 113.3 mm (4.46 inches) of platen travel. Head contact occurred at 119 mm (4.68 inches) of platen travel. On the second side, the Scion achieved a 4.1 SWR prior to head contact at 95.0 mm (3.74 inches) of platen travel. From these tests we believe it is feasible and practicable for smaller vehicles with less initial headroom to meet the requirements. Since both are two-door vehicles, we disagree with Hyundai's assertion that two-door vehicles pose an unreasonable challenge.

We agree with Ford's observations that some vehicles that may appear to be “high roofline” vehicles, but may experience head contact in less platen travel than a “low roofline” vehicle. The 2007 Buick Lucerne, a large full size vehicle reached a maximum SWR of 2.3 at a platen displacement of 110 mm (4.33 inches). The vehicle did not reach the proposed SWR of 2.5. In this test, platen travel at head contact was less than the Crossfire. Therefore, the arguments being made for excluding low roofline vehicles may not be unique to low roofline vehicles. Ford's comments also illustrate the difficulty in identifying what is or is not a low roofline vehicle.

DaimlerChrysler suggested SSF or other vehicle parameters could be used to define low roofline vehicles and exclude them from the headroom requirement. However, we believe that this exclusion is not warranted based on our testing. Moreover, we are concerned about the safety impact of unnecessarily excluding vehicles from the upgraded requirements.

6. Leadtime and Phase-In

NHTSA proposed that manufacturers be required to comply with the new requirements three years after the issuance of the final rule. At that time, based upon vehicle testing, we estimated that 68 percent of the current fleet already complied with the proposed roof strength criteria. We anticipated the proposal would not require fleet-wide roof structural changes and believed the manufacturers had engineering and manufacturing resources to meet the new requirements within that timeframe.

In commenting on the NPRM, vehicle manufacturers and their associations argued that additional leadtime was needed, and that a significantly greater portion of the fleet would require redesign than estimated by the agency. The Alliance, Ford and GM stated that approximately 60 percent of their fleets would need to be redesigned, and Hyundai commented that 75 percent of its vehicles would need changes to comply with the requirements.

Toyota, Ford, GM, Hyundai, Nissan and DaimlerChrysler stated that the agency underestimated the necessary modifications to vehicle design and manufacturing challenges that must be overcome to comply with the proposal. Ford, GM, DaimlerChrysler, and Toyota stated that the challenges are especially true for heavier vehicle over 2,722 kg (6,000 pounds) GVWR which have not been required to meet FMVSS No. 216.

GM and Ford stated that they rely on outside suppliers for advanced high strength material and currently there is an insufficient supply base for high strength steel. They also cited significant manufacturing challenges that must be overcome to adapt ultra high strength steel to the mass production environment. They argued that leadtime with a phase-in is necessary to permit growth in the supply base and allow the manufacturers to resolve manufacturability issues for high volume production requirements.

The vehicle manufacturers generally requested a 3-year leadtime followed by a multi-year phase-in. Most supported a minimum 3-year phase-in. GM requested a 4-year phase-in period, and DaimlerChrysler requested a 5-year phase-in only for vehicles over 3,855 kg (8,500 pounds). The AIAM requested compliance credits for an early phase in, while the Alliance, Ford and Mitsubishi requested carryforward credits. The AIAM and Ferrari requested that small volume manufacturers be permitted to comply at the end of the phase-in due to compliance difficulties, long product cycles and cost penalties associated with running structural changes to vehicle programs.

In commenting on the SNPRM, the Alliance reiterated points made in its comment on the NPRM, stating that the final rule needs to provide at least three years initial leadtime followed by a multi-year phase-in with carryforward credits. It stated that additional time is needed if the agency adopted the proposed head contact criterion, a two-side test requirement, or an SWR higher than 2.5. Ford suggested that if the agency adopted a more stringent requirement than the one it focused on in the NPRM, that vehicles meeting a 2.5 SWR/one-sided test requirement earn compliance credits before and during the phase-in.

Agency Decision/Response

After carefully considering the comments and available information, and for the reasons discussed below, we have decided to adopt different implementation schedules for vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or less, i.e., the vehicles currently covered by FMVSS No. 216, and those with a higher GVWR. The implementation schedules we are adopting are as follows:

Passenger cars, multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less.

We are adopting a phase-in of the upgraded roof crush resistance requirements for these vehicles. The phase-in requirement for manufacturers of these vehicles (with certain exceptions) is as follows:

—25 percent of the vehicles manufactured during the period from September 1, 2012 to August 31, 2013;

—50 percent of the vehicles manufactured during the period from September 1, 2013 to August 31, 2014;

—75 percent of the vehicles manufactured during the period from September 1, 2014 to August 31, 2015;

—100 percent of light vehicles manufactured on or after September 1, 2015.

Credits may be earned during the phase-in, i.e., beginning September 1, 2012, and carried forward through August 31, 2015.

Small volume manufacturers are not subject to the phase-in but must meet the requirements beginning on September 1, 2015. Vehicles produced in more than one stage and altered vehicles must meet the upgraded requirements beginning September 1, 2016.

Multipurpose passenger vehicles, trucks and buses with a GVWR greater than 2,722 kilograms (6,000 pounds) and less than or equal to 4,536 kilograms (10,000 pounds).

All of these vehicles must meet the requirements beginning September 1, 2016,

with the following exceptions. Vehicles produced in more than one stage and altered vehicles must meet the requirements beginning September 1, 2017.

If heavier vehicles are designed to meet the new requirements early, their production volumes are not to be included when calculating the light vehicle fleet phase-in percent compliance. The phase-in schedule for the two fleets are separate.

Our rationale for this implementation schedule is as follows.

As discussed in the FRIA, a significantly larger proportion of the vehicle fleet will require changes than estimated at the time of the NPRM. This

would be true even for a 2.5 SWR/one-sided test requirement, and the proportion is higher for the 3.0 SWR/two-sided requirement. We therefore agree that a combination of approximately three years leadtime plus a multi-year phase-in is appropriate.

In developing the implementation schedule, we have considered costs and benefits. The vast majority of the benefits of the rule come from vehicles with a GVWR of 2,722 kilograms (6,000 pounds) and less. Of the 135 fatalities that will be prevented each year, 133 will come from these lighter vehicles. Moreover, the lighter vehicles are generally redesigned more often than the heavier vehicles. Also, manufacturers are familiar with designing and testing the lighter vehicles to meet the current FMVSS No. 216 requirements.

In order to implement the upgraded requirements in a cost effective manner, we believe it is appropriate to provide approximately three years of leadtime coupled with a 25 percent/50 percent/75 percent/100 percent phase-in for the lighter vehicles, and longer leadtime for the heavier vehicles. The benefits for the heavier vehicles are relatively small, and approximately seven years leadtime will generally permit manufacturers to improve roof strength at the same time they redesign these vehicles for other purposes.

While vehicle manufacturers made varying recommendations for the specific provisions of a phase-in, the phase-in we are adopting for lighter vehicles is within the general range of those recommendations. We recognize that manufacturers argued that longer leadtime should be provided for requirements more stringent than a 2.5 SWR/one-sided test requirement. However, while the 3.0 SWR/two-sided test requirement will increase the number of vehicles requiring redesign and the specific countermeasures that are needed, we believe that approximately three years of leadtime coupled with a 25 percent/50 percent/75 percent/100 percent phase-in provides sufficient time for manufacturers to make these changes. We note that the vehicles likely to present the greatest design challenges under our proposal were the ones with a GVWR above 2,722 kilograms (6,000 pounds), for which we are providing longer leadtime and a lower SWR requirement. Vehicle manufacturers have not provided persuasive evidence that longer leadtime is needed, or that a less stringent requirement should be established for an initial period.

We believe that providing for carry forward credits during the phase-in, but not the earning of advance credits prior to the beginning of the phase-in, balances encouraging early compliance and manufacturer flexibility with also encouraging manufacturers to continue to improve roof strength during the years of the phase-in.

As with a number of other rulemakings, we are establishing special requirements for small volume manufacturers and for vehicles produced in more than one stage and altered vehicles.

Given the leadtime needed for manufacturers to redesign their vehicles to meet the upgraded roof crush requirements, we find good cause for the compliance dates included in this document.

b. Aspects of the Test Procedure

1. Tie-down Procedure

In the NPRM, we proposed to revise the vehicle tie-down procedure in order to improve test repeatability. Specifically, we proposed to specify that the vehicle be secured with four vertical supports welded or fixed to both the vehicle and the test fixture. If the vehicle support locations are not metallic, a suitable epoxy or an adhesive could be used in place of welding. Under the proposal, the vertical supports would be located at the manufacturers' designated jack points. If the jack points were not sufficiently defined, the vertical supports would be located between the front and rear axles on the vehicle body or frame such that the distance between the fore and aft locations was maximized. If the jack points were located on the axles or suspension members, the vertical stands would be located between the front and rear axles on the vehicle body or frame such that the distance between the fore and aft locations was maximized. All non-rigid body mounts would be made rigid to prevent motion of the vehicle body relative to the vehicle frame.

We explained that we believed this method of securing the vehicle would increase test repeatability. Welding the support stands to the vehicle would reduce testing complexity and variability of results associated with the use of chains and jackstands. We also stated that we believed that using the jacking point for vertical support attachment is appropriate because the jacking points are designed to accommodate attachments and withstand certain loads without damaging the vehicle.

Comments

Commenters on the proposed tie-down procedure included the Alliance, DaimlerChrysler, Ford, GM, Toyota, AIAM, Mr. Chu, Hyundai and BMW Group (BMW). A number of commenters agreed with the agency's intention to revise the tie-down procedure for the quasi-static test to improve test repeatability. However, manufacturers raised specific concerns about the proposed procedure. AIAM, Mr. Chu, Hyundai and BMW alternatively recommended retention of the current tie-down procedure. Advocates and SAFE supported the revised tie-down procedure because it has the potential to ensure less vehicle movement during testing.

Ford suggested that the proposed tie-down procedure can cause localized, unrealistic floor pan deformations that can reduce the measured strength of the roof. The Alliance, DaimlerChrysler, Ford, GM and Toyota recommended providing one vehicle support per vehicle pillar. However, they recommended placing the support along the sill, as opposed to the jack points, since they stated that jack points are not designed to withstand the forces generated during a roof crush test. The commenters suggested that this would minimize unwanted body displacement by providing a direct load path during testing which the proposal does not address. For body-on-frame vehicles, DaimlerChrysler also recommended support of the vehicle frame, in addition to the pillar supports, to further prevent sag of the body. In the event that the agency adopts the practice of supporting the body at the pillars, the Alliance, GM, and BMW also requested that a minimum area of support be provided to avoid concentrated loading.

The Alliance, BMW and Ford also had concerns about welding supports to the vehicle body. The commenters stated that welding could decrease the material properties of the body reducing the measured roof strength, and welding might not be practical or possible for non-ferrous or composite materials. BMW alternatively recommended clamping instead of welding, citing concerns about welding certain materials and the possibility of failure of the sills due to the welding. Ford recommended contacting the manufacturer for instructions about welding aluminum sills, if the agency proceeded with the welding protocol.

AIAM, Mr. Chu, Hyundai and Nissan recommended maintaining the existing procedure that supports the entire length of the sill in order to reduce complexities and unwanted body deformation with the tie-down proposal. Nissan suggested supporting the wheelbase at the sill flange pinch welds between the two channels that grab the

pinch weld on the bottom of the sill. The side sill flange would be constrained to prevent transverse body movement when tested. Hyundai recommended that the current procedure be permitted at the manufacturer's option since it believes the revised tie down procedure is burdensome. DaimlerChrysler and Toyota also recommended continuous mounting along the sills suggesting this would prevent unwanted body deformation at the jack point locations.

For vehicles without B-pillars, the Alliance, Ford, and GM recommended that a support be placed at the seam between the doors as if a pillar existed between the doors. The Alliance stated that doors connected without a pillar often have reinforcements to compensate for the structure that would be afforded by a pillar if it were part of the vehicle design, and therefore, the joint between the doors will act as one of the direct load paths from the roof to the rocker. Without a support at the door joint, the Alliance suggested that the roof strength cannot be accurately measured in these types of vehicles.

Agency Response

As part of analyzing the comments on the proposed tie-down procedure for the quasi-static test, the agency conducted analytical simulations using a finite element model on a late model Ford Explorer.

First the agency performed an analysis of the proposed procedure where the vehicle was supported at the jack locations. Two additional models were also developed to evaluate supporting the vehicle body under the pillars and continuously along the length of the body sill, as the commenters suggested.

See

report,

Finite Element Simulation of FMVSS No. 216 Test Procedures,

placed in the docket with this notice.

The Ford Explorer was modeled because it is a body-on-frame

vehicle, and according to the comments, the proposed procedure would not accurately evaluate the roof strength of that type of vehicle. The first Explorer tie-down model followed the NPRM procedure where the vehicle was supported at its jack point locations. This was along the frame mounted inward of the vehicle body sill in the case of the Explorer. The analysis showed that the NPRM procedure produced compression of the body-to-frame rubber body mounts. We believe this tie-down simulation did not accurately evaluate the strength of the roof because the body was not isolated in the simulation. The loading of the body mounts is also unrealistic in a rollover. The results were consistent with Ford's comment that suggested supporting a vehicle by its frame at the body mount locations could cause floor pan deformation and thereby reduce the measured strength of the roof.

A body-on-frame vehicle is constructed by attaching a vehicle body to a rigid frame which supports the drivetrain. At the attachment points, rubber body mounts are used to isolate the body from vibration.

The results of the other simulations (vehicle secured under the pillars and vehicle secured along the rocker/sill) showed higher roof strength than the NPRM procedure. There was nearly a 7 percent increase in roof strength within 127 mm (5 inches) of platen travel when the vehicle's body was supported under the pillars compared to the NPRM procedure. The simulation results using the continuous sill support tie-down showed a 3 percent increase in roof strength compared to the NPRM procedure. Overall, in both simulations, the body sag in the floor pan did not appear to be a concern and produced a more realistic loading of the roof. The load-deformations curves were also similar, whereas the results from the simulation using the NPRM tie-down procedure diverged early in the analysis at approximately 18,000 N or 0.8 SWR.

We note that the full sill tie-down procedure generated a lower peak force when compared to the vehicle supported under the pillars. The simulation for the full sill tie-down procedure did not include any constraints for the Explorer's frame. However, when the vehicle body was supported under each pillar, a number of vertical supports were added to support the mass of the frame. This could explain the slight difference in the maximum strength of the roof. However, we believe the difference is negligible.

After considering the comments and the computer simulations, we decided, for purposes of fleet testing, to revise the tie-down procedure to support the vehicle continuously under the sill. We believe this approach further reduces any variability compared to the Alliance recommendation because the entire wheelbase of the vehicle is supported and not just under each pillar. Also, the peak force difference in the computer models was not a significant issue because both methods addressed the commenters' main concern of inappropriate floor pan deformation. For body-on-frame vehicles, additional supports would be placed under the frame as this constraint was not included in the computer simulation and might account for the difference in peak force. The full sill tie-down procedure is consistent with the existing FMVSS No. 216 requirement supported by AIAM, Mr. Chu, Hyundai, and Nissan.

For the fleet testing,

the vehicle's sill at the body flange weld was fully supported along the wheelbase between two box tubes and securely fixed into place with high strength epoxy. For body-on-frame vehicles, additional supports were placed under the frame to reduce body sag created by an unsupported frame, as recommended by DaimlerChrysler. Epoxy was selected in response to the Alliance, BMW and Ford's comments that welding may adversely alter the vehicle's structure prior to testing. We believe the epoxy will not alter the material properties of the vehicle structure or cause complications for sills made of non-ferrous or composite materials. The revised test procedure provided support for each of the vehicle pillars and provided a stable load path when tested, consistent with the recommendations by the Alliance, DaimlerChrysler, Ford, GM and Toyota. Also, by supporting the vehicle along the wheelbase, which includes the door seam for vehicles without a B-pillar (the joint between the doors), a reactionary surface is provided for the applied load when tested, addressing the Alliance, GM and Ford's concerns.

See

report,

Two-Sided Roof Crush Strength Analysis,

placed in the docket of this notice.

During our evaluation of the tie-down procedure,

dial indicators were placed at the sill below the vehicle's pillars on the opposite side of the platen travel to check for vehicle displacement during the test. The tie-down procedure showed on average less than a millimeter (0.04 inches) of body displacement at all measurement locations, parallel to the direction of platen motion for both unibody and body-on-frame vehicles. For comparison, the agency also tested a Buick Lacrosse that was rigidly supported along the entire wheelbase and compared the result to another Lacrosse test where the sill was supported along the wheelbase only at 152.4 mm (6 inch) increments. The Lacrosse was also supported under the pillars, as recommended by the

Alliance. The results showed that the body displacement was lower for the full sill tie-down when compared to the results where the sill was only partially supported.

The agency measured the sill displacement at three locations along the wheelbase on the side opposite to the force application on the roof, for 13 vehicles. Ten of the tests were single-sided and three were two-sided. The sill displacement ranged from 0 to 2.3 mm (0.09 inches). The VW Jetta achieved the highest SWR level at 5.7 in this data set and experienced almost no sill movement. In the three two-sided tests in this series, conducted with the Subaru Tribeca and two Buick Lacrosses, the agency did not observe any significant difference in sill displacement on the second side compared to the first.

After considering the comments and in light of the testing and simulations, we are adopting the revised tie-down procedure, where the vehicle is supported at the sill, along the entire wheelbase. This procedure reduces vehicle displacement, more accurately measures the strength of the roof, and is more robust than the procedure recommended by the Alliance and its members. Furthermore, the revised test procedure addresses the comments to the NPRM because it supports the vehicle pillars during testing and reduces the likelihood of vertical and horizontal translation of the body.

We note that, in light of the fact that the test procedure is consistent with the current FMVSS No. 216 test procedure while providing improved clarity, the agency has adopted it for use in current FMVSS No. 216

compliance tests. This procedure has been used for 19 fiscal year 2007 and 2008 OVSC compliance tests.

TP-216-05 Laboratory Test Procedure for FMVSS No. 216, November 16, 2006.

2. Platen Angle and Size

In the NPRM, we did not propose to change the test device orientation or the size of the test plate. However, we included a discussion of comments related to test device orientation and size that we had received in response to the October 2001 RFC.

Under the current test procedure specified in FMVSS No. 216, the test plate is tilted forward at a 5-degree pitch angle, along its longitudinal axis, and rotated outward at a 25-degree angle, along its lateral axis, so that the plate's outboard side is lower than its inboard side. The test plate size of 762 mm (30 inches) wide by 1,829 mm (72 inches) long is designed to load the roof over the occupant compartment. The edges of the test plate are positioned based on fixed points on the vehicle's roof. The forward edge of the plate is positioned 254 mm (10 inches) forward of the forwardmost point on the roof, including the windshield trim. We note that, as discussed later in this document, there is a secondary test procedure for certain vehicles with raised roofs or altered roofs, which we proposed to eliminate.

Comments

The agency received numerous comments and recommendations to change the platen test angle and size. A number of the comments were from safety advocacy groups. Some commenters recommending a 2-sided test requirement recommended that we use different criteria for the two tests.

Consumers Union cited comments it had made on the agency's 2001 RFC and the agency's discussion in the NPRM. That commenter noted that it had recommended that the agency modify the test plate load and size. It stated that it continues to believe that the current plate load and size does not reflect real-world rollover conditions. Consumers Union stated that it believes that more of the roof crush force is absorbed by the A-pillar than accounted for by the current or proposed procedure. It recommended that the agency conduct additional studies concerning this issue.

IIHS commented that testing roof crush strength at multiple load angles would add to the meaningfulness of the quasi-static test requirement that NHTSA currently specifies. However, it also stated that in the absence of a range of plate angles, any distinct test angle choice should be supported by evidence that such an angle is representative of a significant percentage of real-world rollovers.

Various commenters recommended that the agency change the platen pitch in ways they believe would better reflect the more aggressive loading angles that are frequently sustained in real-world rollover crashes, particularly for SUVs and pickups. The general recommendation was to increase the pitch angle of the platen to 10 degrees because commenters believed the proposed 5 degree pitch is not realistic.

CAS stated that the pitch angle must be increased to at least 10 degrees to emulate actual rollovers where damage to front fenders is testimony to the fact that in a rollover, the pitch angles are this high. Advocates suggested that vehicles be evaluated at different platen angles, up to and including 10 degrees pitch × 45 degrees roll.

Mr. Chu suggested a series of procedures he believed would best address the plate angle issue. His 6-step procedure would test each front corner of the roof three times, with the roll angle of the plate maintained at 25 degrees, and the pitch angle from 5 to 10 degrees.

Consumers Union and Mr. Friedman encouraged the agency to consider the use of a smaller platen in order to load the A-Pillar and not extensively load the B-pillar. Mr. Friedman submitted two-sided test data published in a recent technical publication using a smaller platen 301 mm (11.8 inches) wide by 610 mm (24 inches) long and at different pitch and roll angles.

The commenter stated that the smaller plate more aggressively loads the A-pillar. It showed the roof achieved a lower SWR on the second side by as much as 40-70 percent compared to the current FMVSS No. 216 procedure.

Friedman D.,

et al.,

“Result From Two Sided Quasi-Static (M216) and Repeatable Dynamic Rollover Test (JRS) Relative to FVMSS 216 Tests,” 20th ESV Conference, Lyon, France, 2007.

Agency Response

After carefully considering the comments, we have decided to maintain the current platen size and the pitch and roll angle. We note that many of the issues raised by the commenters were ones that were also raised in comments on the 2001 RFC.

Prior to issuing the NPRM, the agency conducted a test series to evaluate alternative platen angles using the FMVSS No 216 platen.

A finite element study was first conducted to evaluate a range of platen configurations and to select appropriate conditions for testing. NHTSA tested four vehicle pairs using 5 degree × 25 degree and 10 degree × 45 degree platen angles. The peak SWR from these tests did not demonstrate a consistent pattern between the two test conditions. For two vehicle models, the 10 degree × 45 degree tests generated a higher peak SWR, whereas, the 10 degree × 45 degree tests generated a lower peak SWR in the others. Therefore, the test results were inconclusive.

See

Docket NHTSA 2005-22143-57: Load Plate Angle Determination and Initial Fleet Evaluation.

To help evaluate the comments submitted in the NPRM docket, the agency extended the previous finite element studies to evaluate alternative platen angles in conjunction with a smaller platen.

The finite element model of a 1997 Dodge Caravan was used to evaluate two-sided simulations with a 5 degree × 25 degree orientation on the first side and a 10 degree × 45 degree orientation on the second side. The reduction in peak SWR for using a 10 degree × 45 degree platen angle on a second side test was 18.7 percent. The 18 percent reduction in peak SWR, while significant, is much less than the 40 to 70 percent shown in the test results submitted to the docket. The results were also in line with our two-sided vehicle test results using the 5 degree × 25 degree platen orientation for both sides. On average there was an 8.7 percent reduction of strength on the second side compared to the first. Furthermore, we found an average

difference of approximately 7.1 percent lower peak force for the second side in vehicles under 2,722 kilograms (6,000 pounds) GVWR and 14.9 percent lower peak force for the second side in vehicles over 2,722 kilograms (6,000 pounds) GVWR.

See,

Finite Element Simulation of FMVSS No. 216 Test Procedures,

placed in the docket with this notice.

To evaluate how a smaller platen affects roof strength measurements, the agency also conducted simulations with a smaller 305 × 610 mm (12 × 24 inch) platen using a 10 degree × 45 degree platen angle on a Dodge Caravan model. The results showed an approximate six percent decrease in peak force compared to our baseline results with a larger platen using the same configuration. However, the simulations showed the potential for platen edge-to-

This text is long and has been trimmed here. Open the source document for the complete record.

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.