Federal Motor Vehicle Safety Standards; Child Restraint Systems

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 99-5891]

RIN 2127-AH14

Federal Motor Vehicle Safety Standards; Child Restraint Systems

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation.

ACTION: Request for comments.

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SUMMARY: The agency is issuing this document to obtain information that

will help NHTSA determine whether Safety Standard No. 213, ``Child

Restraint Systems,'' should be amended in response to a petition for

rulemaking from Kathleen Weber of Ann Arbor, Michigan. The petition

concerns the availability of child booster seats for older children

(ages about 4 and older) that can be used in older cars whose rear

seats are equipped with only lap belts instead of both lap and shoulder

belts. To make it easier for child restraint manufacturers to produce

child restraints for these children, the petition asks that Standard

213 be amended such that compliance tests of booster seats may be

conducted with a top tether attached.

In the past, many drivers did not attach tethers when they used

tether-equipped child restraints in vehicles that lack user-ready

tether anchorages. Given that the vehicles in question lack user-ready

tether anchorages, the agency seeks comments on the extent to which

vehicle drivers would attach the booster seat's top tether. The agency

also seeks comments on the extent to which currently available vests,

harnesses, and other restraint systems (e.g., shoulder belt retrofits)

address the problem raised by the petitioner. Comments are requested on

the feasibility of redesigning boosters such that the restraints can

meet Standard 213's requirements when attached to the vehicle with only

a lap belt, and without the use of a tether.

DATES: You should submit your comments early enough to ensure that

Docket Management receives them not later than September 7, 1999.

ADDRESSES: You should mention the docket number of this document in

your comments and submit your comments in writing to: Docket

Management, Room PL-401, 400 Seventh Street, SW, Washington, DC, 20590.

You may call Docket Management at 202-366-9324. You may visit the

Docket from 10 a.m. to 5 p.m., Monday through Friday.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may call

Mike Huntley of the NHTSA Office of Crashworthiness Standards, at 202-

366-0029.

For legal issues, you may call Deirdre Fujita of the NHTSA Office

of Chief Counsel at 202-366-2992.

You may send mail to both of these officials at National Highway

Traffic Safety Administration, 400 Seventh St., SW., Washington, DC.,

20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background

a. The booster seats in question became unavailable after

upgrade to Standard 213

b. Petitioner seeks to make boosters available by allowing them

to be tethered in compliance test

c. The safety concern is that tethers often were not used in

vehicles lacking a user-ready tether anchorage, even by parents who

were aware of the importance of attaching the tether

d. The recent regulation requiring user-ready tether anchorages

to improve tether use will not apply to vehicles manufactured before

September 1999

II. Issues

III. Comments

Appendix A--Calspan Study

APPENDIX B-NHTSA TEST PROGRAM

I. Background

On December 4, 1997, Ms. Kathleen Weber of the University of

Michigan Child Passenger Protection Research Program, submitted a

petition for rulemaking to amend Federal Motor Vehicle Safety Standard

No. 213, ``Child Restraint Systems'' (49 CFR 571.213). The petition,

which NHTSA granted on January 30, 1998, concerns the manufacture of

booster seats that can be used by families using pre-1989 model year

vehicles. These vehicles have only lap belts in rear seating positions.

a. The Booster Seats in Question Became Unavailable After Upgrade

to Standard 213

Booster seats are designed for children who have outgrown a

convertible or toddler child restraint system. They are generally

designed for children who are about 4 to 8 years old. There are two

main types of booster seats currently produced. One type is called a

``shield booster'' due to use of a shield-like barrier to restrain the

upper torso of a child in a crash. Shield boosters attach to the

vehicle by the vehicle's lap belt (Type I belt) or lap belt portion of

a lap and shoulder belt (Type II belt). The other type of booster is

called a ``belt-positioning seat,'' which is a booster designed to use

both portions of a vehicle's Type II belt to restrain the child. A

belt-positioning seat is not directly attached to the vehicle seat, but

is held in place by the child's mass and the vehicle's Type II belt,

which is strapped over the child's lap and torso, just as the Type II

belt is used to restrain an adult occupant. A belt-positioning seat

must not be used with a vehicle's lap belt alone, since the seat lacks

structure or an internal belt to restrain the child's upper torso.

Shield booster seats, which are capable of being used with only a

vehicle's lap belt, were available in the past, but became unavailable

for children weighing over 18 kilograms (kg) (approximately 40 pounds,

lb) subsequent to an upgrade that NHTSA made to the standard pursuant

to the Intermodal Surface Transportation Efficiency Act (``ISTEA'') of

1991 (Pub. L. 102-240). That Act directed NHTSA to initiate rulemaking

on a number of safety matters, including child booster seat safety

(section 250). The legislative

[[Page 36658]]

history for the directive indicated that its impetus was a study

1 that found that shield booster seats then manufactured

could not adequately restrain test dummies representative of the

children for whom manufacturers typically recommended for the seats. In

the study, the boosters could not adequately restrain a 22 kg (48 lb)

test dummy (representing a 6-year-old) when dynamically tested under

Standard 213. The boosters were ineffective at limiting head excursions

to within the requirements of Standard 213, and two of the boosters

failed structurally. The boosters also failed to prevent the ejection

of a 9 kg (20 lb) test dummy (representing a 9-month-old child) in the

dynamic test. These phenomena were observed notwithstanding the

recommendation of some booster seat manufacturers that their seats were

suitable for children weighing from 9 up to 32 kg (20 up to 70

lb).2

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\1\ Calspan Corporation (DOT HS 807 297, May 1988). A detailed

discussion of this study can be found in Appendix A to today's

document.

\2\ Because at that time only a 3-year-old dummy was used in

Standard 213's compliance test, the boosters could meet the standard

when tested with that dummy and were thus certified as complying

with the standard.

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In response to this study and to the ISTEA directive, NHTSA amended

Standard 213 to permit the manufacture of belt-positioning seats, which

were considered to be a new, superior type of booster seat (59 FR

37167, July 21, 1994). Belt-positioning boosters were believed to be

better able than shield boosters at accommodating a wider range of

child sizes. These boosters have since replaced shield boosters in the

marketplace, as many commenters to the rulemaking, including the

petitioner for this document, Kathleen Weber, had hoped they would.

NHTSA also incorporated the 6-year-old and 9-month-old dummies into the

standard's compliance test protocols, to ensure a more thorough

evaluation of the ability of a child restraint to adequately restrain

children recommended for the restraint, as compared to testing done

with only the 3-year-old dummy. Beginning in September 1996, any child

restraint recommended for children weighing over 18 kg (40 lb) must be

able to comply with the standard when tested with the 6-year-old child

dummy (60 FR 35126, July 6, 1995; 60 FR 63651, December 12, 1995).

Comments from manufacturers and others on the proposal to use the

6-year-old dummy in compliance tests did not indicate that shield

boosters manufactured at the time of the rulemaking could not comply.

To the extent there were any shield boosters that could not pass the

standard's requirements with the 6-year-old dummy, NHTSA anticipated

that manufacturers might (1) design their seats to achieve compliance

(such as by raising the height of the shield relative to the child's

torso), (2) relabel shield boosters as being suitable for children

weighing less than 18 kg (and thus avoid testing with the 6-year-old

dummy), or (3) replace production of shield boosters with belt-

positioning boosters. While the latter two responses to the final rule

have occurred, manufacturers have not redesigned shield boosters to

pass Standard 213 with the 6-year-old dummy. Thus, the shield boosters

manufactured today are not recommended for use by children over 18 kg

(40 lb).

b. Petitioner Seeks To Make Boosters Available by Allowing Them To Be

Tethered in Compliance Test

Petitioner does not want to see the renewed sale of shield booster

seats, because she does not believe the restraints provide adequate

upper torso restraint. Instead, the petitioner suggests that Standard

213 be amended to allow--

``hybrid'' toddler/booster restraints (forward facing with

internal harness/high-back belt-positioning booster) to be used by a

(20 kg) 45 lb child in the toddler mode with its internal harness

and installed with a lap belt and top tether strap.

The petitioner is referring to child restraints that can be used

with a Type I (lap) belt and with a Type II (lap/shoulder) belt. An

example of such a seat is Century's Breverra booster car seat, which is

recommended for children 14 to 27 kg (30 to 60 lb). The Breverra has a

removable 5-point harness system. When used with children weighing up

to 18 kg (40 lb), the Breverra is used with the 5-point harness, and

the restraint is secured to the vehicle seat by either a Type I or Type

II belt. (In vehicles equipped with Type II belt systems, a locking

clip may be required for proper installation of the restraint.) This

configuration (using the restraint system with children weighing up to

18 kg (40 lb), and restraining them with the internal 5-point harness)

is what the petitioner refers to as the ``toddler mode.'' The Breverra

is also designed for use as a belt-positioning seat with children 14 to

27 kg (30 to 60 lb). Parents are instructed to remove the 5-point

harness from the booster seat, and to use the car's Type II belt to

restrain the child. Because seats such as the Breverra are designed for

use both as a ``toddler seat'' and as a ``belt-positioning booster

seat,'' petitioner refers to them as ``hybrid'' restraints.

Petitioner seeks to permit hybrid restraints to be certified as

meeting the standard when recommended for children up to 20 kg (45 lb)

in the toddler mode (using the 5-point harness, attached to the vehicle

by lap belt). Currently, restraints recommended for children up to 20

kg are tested with the 6-year-old dummy. Hybrid restraints cannot meet

the head excursion limit, untethered, when tested with the 6-year-old

dummy in the toddler mode (using the 5-point harness). Presumably, they

can meet it tethered.

A number of parties have written to NHTSA in support of the

petition, including Safe Ride News and SafetyBeltSafe (both reiterated

the views of the petitioner). The American Academy of Pediatrics (AAP)

said that a high-back booster would help in physically restraining

young toddlers who can easily escape from Type II belts. The National

Transportation Safety Board (NTSB) expressed concern that the lack of

child restraints for older children complicates efforts to encourage

states to enact legislation to require children to ride in the back

seat. However, NTSB did not support measures that required use of a

tether or retrofitting a vehicle with a rear seat shoulder belt (these

approaches, and others, are discussed further below). NTSB hoped that

NHTSA will ``work with the child restraint manufacturers to expedite

efforts to provide child restraint systems for children who have

outgrown their convertible restraint systems to be used with lap-only

belts.''

c. The Safety Concern Is That Tethers Often Were Not Used in Vehicles

Lacking a User-Ready Tether Anchorage, Even by Parents Who Were Aware

of the Importance of Attaching the Tether

Tether use in vehicles not originally equipped with tether

anchorages has been very low in this country. Because of the low use

rate for tethers, NHTSA amended Standard 213 in 1986 to require

tethered child restraints to pass the 48 kph (30 mph) test without

attaching a tether (51 FR 5335). NHTSA amended the standard because

surveys that had been conducted for the agency consistently showed that

tethered restraints were used in those vehicles without the tether

strap attached more than 80 percent of the time. Seventy-eight (78)

percent of persons not using the tether strap knew that its use was

necessary for their child's protection, but still did not attach the

tether. Given the low level of tether strap use in vehicles lacking a

user-ready tether anchorage and the high level of awareness that the

strap must be used,

[[Page 36659]]

the agency did not believe that a tether strap could continue to be

permitted as a device necessary for the adequate protection of

children.

Child restraint harnesses and vests were not affected by the

rulemaking. This is because the potential for misuse of harnesses and

vests seemed to be significantly less than for tethered child seats.

With child harnesses and vests, it would be obvious to parents that if

the tether were not attached, the child would be completely

unrestrained in a crash. NHTSA also noted that its data on the non-use

and misuse of tethers did not study the extent to which the tethers are

improperly used on harnesses and vests. To date, harnesses and vests

are tested with the tether strap secured.

d. The Recent Regulation Requiring User-Ready Tether Anchorages to

Improve Tether Use Will Not Apply to Vehicles Manufactured Before

September 1999

To promote higher tether use, NHTSA has recently issued a final

rule that requires vehicle manufacturers to install factory-installed,

user-ready tether anchorages (with hardware) in new vehicles, beginning

September 1, 1999. 3 We believe, as do Canada and Australia,

that tether use improves when factory installed tether anchorages are

provided on vehicles as standard equipment. However, the requirement

for user-ready tether anchorages applies to vehicles manufactured on or

after September 1, 1999, and will not apply to the vehicles that are

the subject of the petition (older vehicles with only lap belts in rear

seating positions).

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\3\ The rule also amended Standard 213 to add a 720 millimeter

(mm) (28 inch) head excursion limit for forward-facing child

restraints, which manufacturers may meet by attaching a tether. The

existing 813 mm (32 inch) head excursion requirement will also have

to be met, with the tether unattached, to maximize head protection

even when the tether is not attached by a consumer.

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II. Issues

The agency seeks comments that will help it to assess whether NHTSA

should amend Standard 213 to permit booster seats, and possibly other

child restraint systems, to be tethered in determining compliance with

the head excursion requirements, and possibly with other requirements

as well.

NHTSA notes that the circumstances that gave rise to the petition

are diminishing. Vehicles manufactured in 1989 and after are required

to have Type II (lap and shoulder) belts installed in rear outboard

seating positions, enabling the use of belt-positioning booster seats,

with the Type II belts, for children weighing more than 18 kg. Pre-1989

vehicles are at the root of the issue, because they typically have no

Type II (lap and shoulder) belts in the rear seats. However, these

vehicles are steadily declining in number and eventually will be

replaced by vehicles with rear seat Type II belts.

This document sets forth below a number of requests for comments

and data. For easy reference, the requests are numbered consecutively.

In providing a comment on a particular matter or in responding to a

particular question, commenters should provide any relevant factual

information to support their conclusions, including but not limited to

cost and statistical data, and the source of such information.

Question 1. How Likely Are Tethers To Be Used in Vehicles That Lack

User-Ready Tether Anchorages?

Tether use in vehicles not originally equipped with tether

anchorages has been very low in this country. Are there data that show

that tether use in vehicles not originally equipped with a tether

anchorage will be greater than it has been in the past?

The petitioner's approach would delete the head excursion

requirement when the seat is tested untethered with the 6-year-old

dummy, i.e., in the manner that data show the seat is likely to be used

in a vehicle that did not have an originally-installed tether

anchorage. NHTSA conducted testing at our Vehicle Research and Test

Center (VRTC) in March 1998, to evaluate the performance of various

types of child restraints in limiting the amount of head excursion of

the 6-year-old dummy. The test program is discussed in Appendix B, and

a test report has been placed in the general reference docket for

Standard 213, NHTSA-99-5426. Our testing showed that untethered seats

were unable to meet the head excursion requirement. The seats generally

allowed between 795 and 851 mm (31.29 and 33.52 inches) of head

excursion. Nonuse of the tether will affect the possible advantages of

petitioner's suggested change.

Question 2: Is a Child Better Off in an Untethered Booster or Seated

Directly on the Vehicle Seat and Restrained by a Lap Belt? Are There

Alternative Approaches?

NHTSA's March 1998 testing program showed head excursions of the 6-

year-old dummy of up to 851 mm (33.52 inches) for untethered

restraints. Data are unavailable for head excursions for dummies

restrained only by a lap belt.

A preliminary study conducted by NHTSA, based on data from the

Fatality Analysis Reporting System (FARS) from 1988 through the first 6

months of 1997, compared the experience of unrestrained rear seat

occupants to some children using a lap belt only and to other children

using both lap and shoulder belts. The study found that for children

ages 5-14, use of a lap belt only while seated in a back outboard seat

of a car is 38 percent effective in reducing fatalities and use of a

back seat lap/shoulder belt is 52 percent effective in reducing

fatalities. The study shows that these children appear to derive the

greatest incremental benefit from using back seat lap/shoulder belts

rather than just a lap belt when compared to the other age and sex

groups evaluated in the study. In comparison, NHTSA estimates that

child restraints are potentially 71 percent effective in reducing the

likelihood of death.4

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\4\ Kahane, Charles J. (1986), An Evaluation of the

Effectiveness and Benefits of Safety Seats, U.S. Department of

Transportation, National Highway Traffic Safety Administration, DOT

HS 806 889, p. 305. The agency believes that this figure remains

valid.

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The same study also showed that, based on FARS and Multiple Cause

of Death (MCOD) data from 1988-1994, children ages 5-14 do not have an

increased risk of abdominal injuries compared to occupants in other age

groups. Lap belted and lap/shoulder belted children have abdominal

injury rates slightly higher than unrestrained children in frontal

crashes (12 and 15 per 100, respectively as compared to 9 per 100 for

unrestrained). These rates are at or below the injury rate of lap

belted and lap/shoulder belted occupants of all ages in frontal

crashes. However, the same data indicate that the head injury rate for

children ages 5-14 in the back seat in frontal crashes restrained by a

lap belt only is double that (50 versus 25 per 100) of those children

restrained with a lap and shoulder belt (and thus provided with upper

torso protection similar to what could be expected through the use of

child restraint systems).

Head excursions beyond that limited by Standard 213 reduce the

level of performance now required by 213. However, some believe that

using a lap belt without an upper torso restraint could result in

``seat belt syndrome,'' which refers to bruising across the abdomen,

internal injuries and lower spine fractures which, allegedly, are

caused mainly by a lap belt that is used incorrectly or that moves off

the child's pelvis during a crash. Are children restrained only by a

lap belt experiencing seat belt syndrome? Should we reduce the

protection required in the standard against head

[[Page 36660]]

impacts to broaden the protection against seat belt syndrome?

If there were no head excursion limit when a booster seat is tested

untethered with the 6-year-old dummy, this would seem to require no

more of booster seats than what is expected when the dummy is seated

directly on the vehicle seat and restrained by just a lap belt. An

alternative approach could be to increase Standard 213's head excursion

limit from 813 mm (32 inches) to 838 mm (34 inches) when testing a

booster seat untethered with the 6-year-old dummy. Under that approach,

there would be a limit to head excursion, even in the untethered

condition. Comments are requested on this approach.

Question 3: Should the Test That Evaluates Child Restraint Performance

Without Attaching the Tether Be Deleted for All Restraints, Not Just

Hybrid Toddler/Booster Restraints? Should the Test Be Deleted When

Testing With Dummies Other Than the 6-Year-Old?

If a tether were permitted to be attached when testing with the 6-

year-old dummy, should tethers be attached with testing with the 3-

year-old as well, such as when testing convertible child restraints

(which are usually recommended for children from birth to 18 kg (40

lb))? The agency believes that deleting the test for these other

restraints and in tests with other dummies is inadvisable at this time,

in the absence of data indicating whether tethers would be properly

used. However, what reasons would justify distinguishing between tether

use rates among hybrid boosters and other types of child seats or

otherwise justify why a tether could be attached for some restraints

and not for others?

Question 4: Why Are Shield Boosters No Longer Manufactured for Children

Weighing over 18 kg (40 lb)?

In the March 1998 test program at VRTC, the agency tested four

currently available types of shield booster seats with the 6-year-old

dummy. Two units of one of these shield boosters were tested, and in

each instance, they appeared to meet all performance criteria of

Standard 213, including the head injury criterion (HIC), chest

acceleration limits, and the head and knee excursion limits. Yet, the

booster was recommended for use by children only up to 18 kg (40 lb).

NHTSA later tested 3 other available shield-type booster seats using

the 6-year-old dummy and found that each exceeded the 813 mm (32 inch)

head excursion limit of Standard 213.

NHTSA requests information, particularly from child restraint

manufacturers, concerning the reasons why shield boosters are no longer

marketed for children weighing more than 18 kg (40 lb), especially with

respect to those boosters that appear to meet all performance criteria

of Standard 213. Were some manufacturers unable to certify that the

seats would meet Standard 213's requirements when tested with the 6-

year-old dummy? If they did so conclude, was it solely the head

excursion requirement, or other requirements as well? Were there test

failures, and if so, what were the margins of failure? Can shield

boosters be redesigned to achieve compliance with the standard? Why

have manufacturers not redesigned these boosters to achieve compliance?

Question 5: What Is the Feasibility of Redesigning Hybrid/Toddler

Booster Restraints Such That the Restraint Can Be Certified for Use

With Older Children, Without the Use of a Tether?

NTSB hoped that NHTSA will ``work with the child restraint

manufacturers to expedite efforts to provide child restraint systems

for children who have outgrown their convertible restraint systems to

be used with lap-only belts.'' NHTSA requests comments on the

feasibility of designing a hybrid booster seat such that the booster

can meet the current requirements of Standard 213 in the ``toddler

mode'' when tested with the 6-year-old dummy, and when attached to the

standard seat assembly with just a lap belt and without a tether.

Question 6: Is the Suggested Amendment Warranted When There Are

Products Now Available for Older Children That May Perform Better Than

a Tethered Seat at Limiting Head Excursion?

E-Z-On Products, Inc., manufactures vest and harness restraint

systems for use with a lap belt and tether. Vests and harnesses are

``child restraint systems'' under Standard 213 and are certified as

meeting all requirements of the standard.

The vest and harness systems employ a top tether to meet Standard

213's requirements. As explained above, Standard 213 permits a tether

on a vest or harness system (both are referred to as ``harnesses'' in

the standard) to be attached in the 48 km/h (30 mph) test, but does not

allow a tether to be attached on a conventional child restraint system

(such as a convertible child restraint or a high-back booster, such as

the Breverra). The reason for the different treatment is because it is

more obvious that a tether needs to be attached with vests and

harnesses than it is with conventional child seats. If a tether were

not used for a vest or harness, it would be clear to the parent that

the child's upper torso would have no restraint.

The E-Z-On Vest is designed to slip over the child, with a back

zipper closure. The vest is custom-made, using the child's waist

measurement. E-Z-On's Universal Harness is in the shape of an upside

down ``Y.'' There are two straps at the bottom of the upside down ``Y''

with loops at each end, that the lap belt is threaded through. The

upper part of the upside down ``Y'' has a tether hook which attaches to

the vehicle's tether anchor. E-Z-On has informed NHTSA that its vest

and harness systems are readily available through its distributors. A

vest or harness can be shipped to the consumer within 2 weeks. The

price of the vest is approximately $73 to $95, a cost comparable to

that of convertible seats. The harness costs approximately $45.

NHTSA's March 1998 test program at VRTC evaluated the performance

of various types of child restraints, including vests and harnesses,

hybrid boosters and convertible restraints, in limiting the amount of

head excursion of the 6-year-old dummy (see Appendix B). In brief, the

tethered vest and harness performed much better than the tethered

hybrid booster or tethered convertible restraint at limiting head

excursion. Test data for the tethered restraints were as follows:

Table 1.--Summary of Sled Test Results for Tethered Restraints

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Head Knee

Restraint configuration HIC 3 ms chest excursion excursion Test No.

clip (G) (mm) (mm)

----------------------------------------------------------------------------------------------------------------

FMVSS No. 213 limit................... 1000 60 813 914

Century Breverra Contour/5-pt. Harness 332 38.9 760.22 904.49 UMP03

Lap Belt w/Top Tether.

Century Breverra Contour/5-pt. Harness 307 40.5 718.82 880.62 UMP05

Lap Belt w/Top Tether.

E-Z ON 86-Y Harness Lap Belt w/Top 463 52.5 495.30 540.26 UMP07

Tether.

[[Page 36661]]

E-Z ON 103Z Vest Lap Belt w/Top Tether 702 59.3 558.29 635.76 UMP08

E-Z ON 86-Y Harness Lap Belt w/Top 461 52.9 473.71 539.75 UMP09

Tether.

Britax Roundabout Lap Belt w/Top 270 42.3 622.55 798.83 UMP11

Tether.

Britax Roundabout Lap Belt w/Top 303 43.4 574.04 736.09 UMP13

Tether.

Britax Elite Lap Belt w/Top Tether.... 554 51.2 640.08 782.32 UMP15

Britax Elite Lap Belt w/Top Tether.... 614 58.9 580.39 719.84 UMP17

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Based on this test program, NHTSA believes that vests and harnesses

could address petitioner's concerns and those of the other parties. The

E-Z-On Vest, with a back zipper closure, could address AAP's desire for

a product that can restrain young toddlers who have reached 18 kg (40

lb), but who are too immature behaviorally to use Type II belts. There

may be perceived drawbacks to vests and harnesses. A vest may not be as

convenient as a hybrid booster. The vest wraps around the child's torso

and has to be unclipped from the tether mounting strap to be placed on

a child. Also, vests and harnesses do not ``look like'' traditional

child restraint systems so they might not be as readily accepted by

some consumers as a tethered hybrid seat might be. Yet, owners of older

vehicles who are seeking any product to fix a perceived problem

concerning their youngsters may be more motivated to accept a harness

than consumers generally.

NTSB did not support measures that required use of a tether, given

the high non-use rates of tethers in this country. Yet, the likelihood

that parents will attach the tether on a harness could be higher than

that for conventional child seats, given that it would be more obvious

to a parent that the tether has to be attached on a vest or harnesses

than on a restraint such as a hybrid booster, which would be designed

to be used both with and without a tether, depending on the size of the

child occupant.

While the hybrid booster might be preferred by some consumers over

a vest or harness because of the expectations of consumers as to what a

child restraint system ought to look like, an untethered hybrid booster

does not restrict head excursion as well as a tethered vest or harness.

Question 7: Would Adoption of the Suggested Amendment Inappropriately

Encourage Some Parents To Position Restraints in the Center Rear

Seating Position?

Petitioner only addressed the need of consumers with pre-1989 cars,

but adoption of the suggested amendment could also affect the

preference of parents who wish to install a booster seat in the center

rear position. The center rear position typically has only a Type I

(lap) belt, not a Type II (lap and shoulder) belt system. Some of these

parents may welcome having booster seats that can be used in the center

rear seat with only a Type I belt. However, optimal performance of the

restraint is dependent on attachment of the tether. An untethered seat

in the center rear seat is not likely to perform as effectively as an

untethered belt-positioning booster used at the outboard seating

position with a Type II belt system. Would the suggested amendment

encourage consumers to move belt-positioning seats from outboard

seating positions to the center rear seat? How likely will consumers

attach a tether 5 when using the seat with children weighing

more than 18 kg (40 lb)?

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\5\ Our March 1999 final rule excludes belt-positioning seats

from the head excursion limit that requires a tether on the child

restraint. Thus, a belt-positioning seat that is not also a hybrid

toddler seat might not even have a tether.

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Question 8: What Is the Feasibility of Retrofitting a Rear Seat

Shoulder Belt in Pre-1989 Vehicles?

Retrofitting vehicles with a rear seat shoulder belt is another

option. While this approach is more expensive than installing a tether

anchorage (assuming there are structural elements for the tether

anchorage already in the vehicle), a shoulder belt can benefit children

who have completely outgrown a child restraint, and can also benefit

adults, seated in the rear. Many vehicle manufacturers offer shoulder

belt kits for rear seating positions, although availability and cost of

these kits vary widely. Because of the long term benefits associated

with this option as described above, we have suggested this approach to

many consumers who have contacted the agency in search of alternatives.

The majority of these consumers were unaware that vehicle manufacturers

offered such retrofit kits, and were generally very receptive to having

the retrofit kits installed in their vehicles. A minority expressed

reservations given the disproportionate cost of the retrofit kit parts

and installation when compared to the limited value of their older

vehicle.

III. Comments

How Do I Prepare and Submit Comments?

Your comments must be written and in English. To ensure that your

comments are correctly filed in the Docket, please include the docket

number of this document in your comments.

Your comments must not be more than 15 pages long. (49 CFR 553.21).

We established this limit to encourage you to write your primary

comments in a concise fashion. However, you may attach necessary

additional documents to your comments. There is no limit on the length

of the attachments.

Please submit two copies of your comments, including the

attachments, to Docket Management at the address given above under

ADDRESSES.

How Can I Be Sure That My Comments Were Received?

If you wish Docket Management to notify you upon its receipt of

your comments, enclose a self-addressed, stamped postcard in the

envelope containing your comments. Upon receiving your comments, Docket

Management will return the postcard by mail.

How Do I Submit Confidential Business Information?

If you wish to submit any information under a claim of

confidentiality, you should submit three copies of your complete

submission, including the information you claim to be confidential

[[Page 36662]]

business information, to the Chief Counsel, NHTSA, at the address given

above under FOR FURTHER INFORMATION CONTACT. In addition, you should

submit two copies, from which you have deleted the claimed confidential

business information, to Docket Management at the address given above

under ADDRESSES. When you send a comment containing information claimed

to be confidential business information, you should include a cover

letter setting forth the information specified in our confidential

business information regulation. (49 CFR part 512.)

Will the Agency Consider Late Comments?

We will consider all comments that Docket Management receives

before the close of business on the comment closing date indicated

above under DATES. To the extent possible, we will also consider

comments that Docket Management receives after that date.

How Can I Read the Comments Submitted by Other People?

You may read the comments received by Docket Management at the

address given above under ADDRESSES. The hours of the Docket are

indicated above in the same location.

You may also see the comments on the Internet. To read the comments

on the Internet, take the following steps:

(2) Go to the Docket Management System (DMS) Web page of the

Department of Transportation (http://dms.dot.gov/).

(3) On that page, click on ``search.''

(4) On the next page (http://dms.dot.gov/search/), type in the

four-digit docket number shown at the beginning of this document.

Example: If the docket number were ``NHTSA-1999-1234,'' you would type

``1234.'' After typing the docket number, click on ``search.''

(5) On the next page, which contains docket summary information for

the docket you selected, click on the desired comments.

You may download the comments. However, since the comments are

imaged documents, instead of word processing documents, the downloaded

comments are not word searchable.

Please note that even after the comment closing date, we will

continue to file relevant information in the Docket as it becomes

available. Further, some people may submit late comments. Accordingly,

we recommend that you periodically check the Docket for new material.

Appendix A--Calspan Study

Both of the rules that amended Standard 213 to permit the

manufacture of belt-positioning booster seats and to adopt new test

dummies into the standard for compliance tests responded to sections

2500-2509 of the Intermodal Surface Transportation Efficiency Act of

1991 (Pub. L. 102-240), which directed NHTSA to initiate rulemaking on

a number of safety matters, including child booster seat safety

(Sec. 2503). The legislative history for the directive indicated that

the directive evolved in large part from the findings of a study

entitled, ``Evaluation of the Performance of Child Restraint Systems,''

performed for NHTSA by the Calspan Corporation (DOT HS 807 297, May

1988). Congress believed that the study showed that some booster seats

``may not restrain adequately a child in a crash . . . .'' Senate

Committee on Commerce, Science, and Transportation, S. Rep. No. 83,

102d Cong., 1st Sess. 6, 18 (1991). Concerns about shield boosters had

arisen from the recommendations by child restraint manufacturers about

which children could appropriately use a particular booster. Particular

designs or models of boosters were typically recommended for a broad

range of children, often for children weighing from 9 to 32 kg (20 to

70 lb). At the time of the study, such a child restraint was tested for

compliance with Standard 213 with just the 3-year-old (15 kg) (33

pound) dummy. So tested, these restraints met Standard 213. However,

there were questions whether the boosters could provide adequate

protection for children at the extremes of the weight ranges that had

been recommended by the manufacturer as being suitable for the

restraint, i.e., those ranging from nine-month-old infants (average

weight 9 kg) to 6-year-old (22 kg) and older children.

In the Calspan program, the nine-month-old infant and the 6-

year-old child dummies were used in addition to the 3-year-old

dummy. The Calspan research program tested all 11 models of booster

seats that were on the market during the summer of 1987. In tests

with the 6-year-old dummy, Standard 213's 813 mm (32 inch) head

excursion limit was exceeded by 10 out of 11 booster seat models,

with measurements in the range from 813 to 899 mm (32.0 to 35.4

inches). One model ejected the dummy.

Following the Calspan study, NHTSA conducted additional research

on boosters. Nine booster seats were tested with the three dummies

used in the Calspan study. The seats met the performance measures of

Standard 213 when tested with the 3-year-old dummy. However, 7 of 9

allowed excessive head excursions with the 6-year-old dummy, and two

of the seats also had structural failures with the dummy.

``Evaluation of Booster Seat Suitability for Children of Different

Ages and Comparison of Standard and Modified SA103C and SA106C Child

Dummies,'' VRTC-89-0074, February 1990.

Appendix B--NHTSA Test Program

NHTSA developed and conducted a test program at VRTC from March

16-20, 1998, to evaluate the performance of various types of child

restraints in restricting the amount of head excursion of the 6-

year-old dummy. In developing this test program, NHTSA asked child

restraint manufacturers and the NTSB for suggestions as to which

approaches and products should be evaluated. One objective of this

test program was to obtain baseline information on the dynamic

performance of a ``typical'' shield-type booster seat, tested with

the 6-year-old dummy while secured to the vehicle seat by a lap belt

only. It is the presumed inability of this type of seat to meet the

813 mm (32 inch) head excursion requirement of Standard 213 that has

apparently resulted in child restraint manufacturers limiting these

restraints to use for children weighing no more than 18 kg (40 lb).

Pre-test discussions with restraint manufacturers confirmed that

Standard 213's head injury criterion (HIC), chest acceleration, and

knee excursion parameters did not pose concerns when testing this

type of restraint with the 6-year-old dummy. Rather, because of the

increase in height and weight of the 6-year-old dummy as compared to

the 3-year-old dummy--1168 versus 965 mm standing height (46 versus

38 inches), and 22 versus 15 kg in weight (48 versus 33 lb)--the

shield portion of the restraint apparently does not provide adequate

upper torso restraint to limit the head excursion within acceptable

limits when subjected to Standard 213's dynamic test. NHTSA chose

the Cosco Grand Explorer as a representative shield-type booster for

this baseline test.

The test program also evaluated a representative high-back belt-

positioning booster seat, utilizing its internal 5-point harness,

secured to the vehicle seat by a lap belt and a top tether. This

represents the specific configuration recommended in the Weber

petition. NHTSA chose the Century Breverra, which comes with an

optional top tether, as a representative seat for the test program.

NHTSA also tested a few convertible seats. Pre-test

conversations with restraint manufacturers indicated that there may

be some convertible restraints that are equipped with tethers that

may also perform adequately when attached to the vehicle seat with a

lap belt only, when restraining the 6-year-old dummy. Not all

convertibles are equipped with a top tether strap, and not all

convertible seats will be able to accommodate the 6-year-old dummy.

Britax Child Safety, Inc. indicated that they currently manufacture

two convertible restraints, the ``Roundabout'' which comes with a

standard top tether, and the ``Elite'' which comes with an optional

top tether attachment, which they felt would perform satisfactorily

in a crash test with the 6-year-old dummy with the restraint secured

to the vehicle seat by a lap belt and top tether. Accordingly, NHTSA

included each of these

[[Page 36663]]

convertible restraints in the subject test program.

Currently, the only commercially available products that are

marketed specifically for children weighing over 18 kg (40 lb) and

secured with a lap belt only are the Y-harness and vest systems

produced by E-Z On Products. Both of these systems require the use

of a top tether. The Y-harness system consists of two shoulder

straps which extend from the top tether anchorage, with looped ends

to allow the vehicle lap belt to be routed through and fastened over

the pelvic area. Similarly, the tether strap is attached to the vest

system by attaching the two snap hooks on end of the tether strap to

rings located on the shoulders of the vest, and the vehicle lap belt

is threaded through the web loops on the bottom of each side of the

vest. Both the Y-harness and the vest systems were included in the

test program for evaluation.

The dynamic sled tests were conducted at NHTSA's Vehicle

Research and Test Center, (VRTC), and were based on the test

conditions and procedures prescribed in S6 of Standard No. 213.

However, it must be emphasized that this test program was intended

for research only and did not precisely replicate compliance

testing. The VRTC tests evaluated the ability of the restraints at

limiting head excursion, HIC, chest acceleration, and knee

excursion. The test conditions were fixed throughout the sled test

series, with the only variable being the particular restraint being

tested and its attachment method (i.e. tethered or untethered). With

the exception of the baseline test utilizing the Cosco Grand

Explorer shield booster seat, each restraint was tested in each

attachment configuration on two separate sled runs to enhance the

repeatability of the test results. Two Cosco Grand Explorer

restraints were tested, but on the same sled run versus separate

sled runs as with the other restraints.

All tests were conducted using the 6-year-old dummy, and each of

the restraints--whether tethered or untethered--was attached to the

vehicle test seat using a lap belt only. Standard 213's limits are

as follows: HIC--1000; chest acceleration--60g; head excursion--813

mm (32 inches); and knee excursion--914 mm (36 inches). The full

test results are provided in Table 2. It is important to note that

in each of the tests conducted, values for both the HIC and chest

acceleration parameters were typically significantly below the

established limits prescribed in Standard 213 and that none exceeded

the maximum allowable limits.

Table 2.--Summary of Sled Test Results for All Restraints

----------------------------------------------------------------------------------------------------------------

Head Knee

Restraint configuration HIC 3 ms chest excursion excursion Test No.

clip (G) (mm) (mm)

----------------------------------------------------------------------------------------------------------------

FMVSS No. 213 limit................ 1000 60 813 914

Cosco Grand Explorer Lap Belt w/Sm. 424 32.9 697.74 614.17 UMP01

Shield.

Cosco Grand Explorer Lap Belt w/Sm. 417 32.2 748.79 660.15 UMP02

Shield.

Century Breverra Contour/5-pt. 332 38.9 760.02 904.49 UMP03

Harness Lap Belt w/ Top Tether.

Century Breverra Contour/5-pt. 273 30.8 851.41 925.83 UMP04

Harness Lap Belt; No Top Tether.

Century Breverra Contour/5-pt. 307 40.5 718.82 880.62 UMP05

Harness Lap Belt w/ Top Tether.

Century Breverra Contour/5-pt. 243 50.2 NA NA UMP06

Harness Lap Belt; No Top Tether *.

E-Z ON 86-Y Harness Lap Belt w/Top 463 52.5 495.30 540.26 UMP07

Tether.

E-Z ON 103Z Vest Lap Belt w/Top 702 59.3 558.29 635.76 UMP08

Tether.

E-Z ON 86-Y Harness Lap Belt w/Top 461 52.9 473.71 539.75 UMP09

Tether.

E-Z ON 103Z Vest Lap Belt w/Adj. 315 35.9 713.23 597.92 UMP10

CAM-Wrap.

Britax Roundabout Lap Belt w/Top 270 42.3 622.55 798.83 UMP11

Tether.

Britax Roundabout Lap Belt; No Top 477 39.3 810.26 895.60 UMP12

Tether.

Britax Roundabout Lap Belt w/Top 303 43.4 574.0 736.09 UMP13

Tether.

Britax Roundabout Lap Belt; No Top 425 36.1 794.77 864.36 UMP14

Tether.

Britax Elite Lap Belt w/Top Tether. 554 51.2 640.08 782.32 UMP15

Britax Elite Lap Belt; No Top 377 39.2 820.17 867.66 UMP16

Tether.

Britax Elite Lap Belt w/Top Tether. 614 58.9 580.39 719.84 UMP17

Britax Elite Lap Belt; No Top 377 43.1 821.69 878.08 UMP18

Tether.

Century Breverra Contour/5-pt. 299 31.2 843.79 917.96 UMP19 (Repeat of

Harness Lap Belt; No Top Tether UMP06)

(Repeat of UMP06).

----------------------------------------------------------------------------------------------------------------

* HIC based on head contact w/CRS as dummy slipped out of failed 5-pt. harness.

While NHTSA anticipated that shield-type boosters could not meet

the 32-inch head excursion limit of the standard when tested with

the 6-year-old dummy, test results showed that when tested in this

configuration, the Cosco Grand Explorer shield booster seats used

for the baseline testing satisfactorily limited head excursion to

under 762 mm (30 inches) in both instances. In addition, knee

excursion was measured to be 254 to 279 mm (10-11 inches) below the

914 mm (36 inch) limit. These test results are in direct contrast

with the Calspan and VRTC studies (see Appendix A, supra) conducted

in support of NHTSA's ISTEA rulemakings on booster seats.

Following conduct of the baseline test with the shield-type

booster seat, the agency tested the hybrid boosters and the

convertible seats both with and without the top tether strap. In the

tethered configuration, head excursion was measured to be below 762

mm (30 inches), and knee excursion was measured to be below the 914

mm (36 inch) limit (although only marginally so in one instance

(904.49 mm) (35.61 inches)). However, in each of the test runs

conducted using the untethered configuration, head and knee

excursions beyond the respective 813 and 914 mm (32 and 36 inch)

limits were measured, with marginal reductions in both the HIC and

chest acceleration parameters. It should be noted that a total of

three test runs was conducted using the untethered configuration, as

the test dummy slipped out of the child restraint during the second

test run due to a failure of the 5-point harness, voiding the

measurement of head and knee excursion. Interestingly, a comparison

between the untethered shield-type booster used in the baseline

testing and the tethered hybrid booster (forward facing with

internal harness/high-back belt-positioning booster) indicates that

the untethered shield booster performs marginally better (on

average) with respect to limiting head excursion and significantly

better with respect to limiting knee excursion than the hybrid

booster.

Two convertible restraints were evaluated in the same manner,

first with a top tether strap attached and then without. In the

tethered configuration, the Britax Roundabout limited head excursion

to 622.3 and 574.04 mm (24.5 and 22.6 inches) in the two tests

performed, well below the 813 mm (32 inch) limit prescribed in the

standard and also well below the results observed in the baseline

test with the shield-type booster. Knee excursion measurements were

also well below the established limit. However, whereas the

untethered hybrid toddler/booster restraint configuration resulted

in unacceptable head and knee excursions, the untethered Roundabout

configuration limited both head and knee excursion within acceptable

limits (although only marginally

[[Page 36664]]

with respect to head excursion in the first test at 810.26 mm (31.90

inches)). Additionally, while the untethered hybrid toddler/booster

restraint tests resulted in reduced HIC and chest acceleration

measurements, the untethered Roundabout tests resulted in reduced

chest acceleration measurements but increased HIC values.

The second convertible restraint, the Britax Elite, demonstrated

similar results. In the tethered configuration, head excursion was

limited to 640.08 and 580.39 mm (25.2 and 22.85 inches) in the two

tests performed, again well below the 813 mm limit prescribed in the

standard and also well below the results observed in the baseline

test with the shield-type booster. Knee excursion measurements were

also well below the established limit. However, each of the tests

conducted in the untethered configuration resulted in head excursion

measurements that marginally (820.02 and 821.69 mm) (32.29 and 32.35

inches) exceed the 813 mm limit, while knee excursion measurements

remained within acceptable limits.

The two different E-Z On products, the Y-harness and the vest,

are the only products currently marketed for children over 18 kg (40

lb) that do not require the use of a shoulder harness to attach to

the vehicle. Both of these systems require the use of a tether. Test

results show that the Y-harness system dramatically limited head

excursion to 495.3 and 473.71 mm (19.5 and 18.65 inches) on the two

tests, or approximately 33 percent below the 813 mm limit prescribed

in the standard, and significantly below the other tethered systems.

Knee excursion was also limited to values well below established

limits.

E-Z On markets two different styles of the vest system. The

first is an adjustable vest, which can be adjusted for fit as the

child grows via three different zipper locations on the back of the

vest. This was not used in this test program, as the vest, when

configured in its smallest size, was still too large to properly fit

the 6-year-old test dummy. E-Z On also manufactures sized vests,

provided to the consumer based on anatomical measurements of the

child as provided to E-Z On. NHTSA utilized a fitted vest in this

testing program, although it should be noted that the vest provided

by the manufacturer for this testing was very tight on the 6-year-

old dummy, and the next larger size would likely have provided a

better fit. The E-Z On vest system was tested utilizing a top tether

strap. The head and knee excursion values were both well below

established limits. The chest acceleration was 59.3 g, marginally

below the limit of 60 g. This high value for chest acceleration may

be partially attributable to the very snug fit of the vest on the

test dummy.

Given the excessive head excursion measured in 17 of the 20

tests performed in the Calspan and VRTC studies, combined with the

assumption that child restraint manufacturers are not currently

marketing shield-type booster seats for children over 18 kg due to

an inability to meet the head excursion requirement when testing

with the 6-year-old dummy, NHTSA chose to include only one

representative shield-type booster seat (the Cosco Grand Explorer)

to serve as a baseline test for the current test program. However,

given the favorable results with respect to both head and knee

excursion parameters seen with this seat as noted above, NHTSA

conducted a second set of testing to evaluate three other currently

available shield-type booster seats (the Gerry Double Guard, Evenflo

Sidekick, and Fisher Price T-Shield). As before, each seat was

tested twice, on separate test runs, to enhance the repeatability of

the test results. In each instance, the measured head excursion

significantly exceeded the 813 mm (32 inch) limit of Standard 213,

ranging from 876.3 to 1016 mm (34.5 to 40.0 inches). Full test

results are provided in Table 3. These results more closely parallel

those recorded in the earlier tests conducted by Calspan and VRTC.

Physical examination of each of the four shield-type booster seats

tested in this test program revealed no obvious, discernable

variations in construction, i.e., height of the shield, etc., that

would explain the difference in performance of the Cosco Grand

Explorer versus the others with respect to head excursion.

Table 3.--Additional Shield Booster Tests

----------------------------------------------------------------------------------------------------------------

Head Knee

Restraint configuration HIC 3 ms chest excursion excursion Test No.

clip (G) (mm) (mm)

----------------------------------------------------------------------------------------------------------------

FMVSS No. 213 limit.................. 1000 60 813 914 ..................

Gerry Double Guard Lap Belt w/sm. 748 35.8 979.9 825.5 UMP21

Shield.

Evenflo Sidekick Lap Belt w/sm. 721 37.8 873.8 762.0 UMP22

Shield.

Fisher Price T-Shield Lap Belt w/sm. 349 26.1 927.1 767.1 UMP23

Shield.

Evenflo Sidekick Lap Belt w/sm. 820 35.9 876.3 749.3 UMP24

Shield.

Gerry Double Guard Lap Belt w/sm. 780 34.6 1016 838.2 UMP25

Shield.

Fisher Price T-Shield Lap Belt w/sm. 525 31.5 955.0 784.9 UMP26

Shield.

----------------------------------------------------------------------------------------------------------------

Issued on June 29, 1999.

L. Robert Shelton,

Associate Administrator for Safety Performance Standards.

[FR Doc. 99-17235 Filed 7-6-99; 8:45 am]

BILLING CODE 4910-59-P