Anthropomorphic Test Devices; THOR 50th Percentile Adult Male Test Dummy; Incorporation by Reference

Federal RegisterSep 7, 2023

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 572

[Docket No. NHTSA-2023-0031]

RIN 2127-AM20

Anthropomorphic Test Devices; THOR 50th Percentile Adult Male Test Dummy; Incorporation by Reference

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to amend NHTSA's regulations to include an advanced crash test dummy, the Test Device for Human Occupant Restraint (THOR) 50th percentile adult male (THOR-50M). The dummy represents an adult male of roughly average height and weight and is designed for use in frontal crash tests. NHTSA plans to issue a separate NPRM to amend Federal Motor Vehicle Safety Standard (FMVSS) No. 208, “Occupant crash protection,” to specify the THOR-50M as an alternative (at the vehicle manufacturer's option) to the 50th percentile adult male dummy currently specified in FMVSS No. 208 for use in frontal crash compliance tests.

DATES:

You should submit your comments early enough to be received not later than November 6, 2023.

Proposed Effective Date:

Since this rulemaking action would not impose requirements on anyone, we are proposing that the final rule would be effective on publication in the

Federal Register

ADDRESSES:

You may submit comments electronically to the docket identified in the heading of this document by visiting the Federal eRulemaking Portal at

http://www.regulations.gov.

Follow the online instructions for submitting comments.

Alternatively, you can file comments using the following methods:

•

Mail:

Docket Management Facility: U.S. Department of Transportation, 1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.

•

Hand Delivery or Courier:

West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, between 9 a.m. and 5 p.m. ET, Monday through Friday, except Federal holidays. To be sure someone is there to help you, please call (202) 366-9826 before coming.

•

Fax:

(202) 493-2251.

Instructions:

All submissions must include the agency name and docket number or Regulatory Information Number (RIN) for this rulemaking. For detailed instructions on submitting comments and additional information on the rulemaking process, see the Public Participation heading of the Supplementary Information section of this document. Note that all comments received will be posted without change to

http://www.regulations.gov,

including any personal information provided. Please see the Privacy Act heading below.

Docket:

For access to the docket to read background documents or comments received, go to

http://www.regulations.gov.

You may also access the docket at 1200 New Jersey Avenue SE, West Building, Room W12-140, Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal Holidays. Telephone: 202-366-9826.

Confidential Business Information:

If you claim that any of the information in your comment (including any additional documents or attachments) constitutes confidential business information within the meaning of 5 U.S.C. 552(b)(4) or is protected from disclosure pursuant to 18 U.S.C. 1905, please see the detailed instructions given under the Public Participation heading of the Supplementary Information section of this document.

Privacy Act:

Please see the Privacy Act heading under the Regulatory Analyses section of this document.

FOR FURTHER INFORMATION CONTACT:

For non-legal issues, you may contact Mr. Garry Brock, Office of Crashworthiness Standards, Telephone: (202) 366-1740; Email:

Garry.Brock@dot.gov;

Facsimile: (202) 493-2739. For legal issues, you may contact Mr. John Piazza, Office of Chief Counsel, Telephone: (202) 366-2992; Email:

John.Piazza@dot.gov;

Facsimile: (202) 366-3820. The address of these officials is: the National Highway Traffic Safety Administration, 1200 New Jersey Avenue SE, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary

II. Background

III. Design, Construction, and Instrumentation

A. Anthropometry

B. Technical Data Package

C. Head and Face

D. Neck

E. Chest

1. Design

2. Instrumentation

F. Shoulder

1. Alternate Shoulder Specification

2. Shoulder Slip

G. Hands

H. Spine

I. Abdomen

J. Pelvis

K. Upper Leg

L. Knee

M. Lower Leg

N. Data Acquisition System

IV. Biofidelity

V. Qualification Tests

A. Head Impact

B. Face Impact

C. Neck

D. Upper Thorax

E. Lower Thorax

F. Abdomen

G. Upper Leg

H. Knee and Lower Leg

VI. Repeatability and Reproducibility

A. Qualification Tests

B. Sled Tests

1. Methodology

2. Thoracic Injury Criteria Development Sled Tests

3. Low-Speed Belted Sled Tests

4. Low-Speed Unbelted Sled Tests

VII. Overall Usability and Performance

A. Assembly and Qualification

B. Durability and Maintenance

1. Elevated Energy Qualification Test Series

2. Oblique OMDB Test Series

3. FMVSS No. 208 Unbelted Vehicle Crash Tests

C. Sensitivity to Restraint System Performance

VIII. Intellectual Property

IX. Consideration of Alternatives

X. Lead Time

XI. Incorporation by Reference

XII. Regulatory Analyses

XIII. Public Participation

Proposed Regulatory Text

I. Executive Summary

This document proposes to amend NHTSA's regulation on anthropomorphic test devices—or, more colloquially, crash test dummies—to include an advanced crash test dummy, the Test Device for Human Occupant Restraint (THOR) 50th percentile adult male (THOR-50M). The dummy represents an adult male of roughly average height and weight and is designed for use in frontal crash tests.

Crash test dummies are complex instruments that simulate the response of a human occupant in a crash. Each type of test dummy is designed for use in specific types of crashes (for instance, frontal or side) and is instrumented with sensors to measure the forces that would have been experienced by a human occupant in a similar crash in the real world. These measurements are then used to assess the potential for injury.

Crash test dummies are used by NHTSA and by the broader vehicle safety community in a variety of ways.

NHTSA uses crash test dummies to test vehicles for compliance with Federal Motor Vehicle Safety Standards (FMVSSs) and to determine vehicle crashworthiness ratings for the New Car Assessment Program's (NCAP) 5-Star Safety Ratings, as well as to conduct vehicle safety research. Crash test dummies are also used by regulatory authorities in other countries and regions, third-party vehicle rating programs, motor vehicle and equipment manufacturers, and others to evaluate vehicle safety and design safer vehicles and equipment.

The dummies NHTSA currently uses in FMVSS compliance testing and NCAP are documented in 49 CFR part 572, Anthropomorphic Test Devices. Part 572 sets out detailed design information, including engineering drawings and procedures for assembly and inspection. These are intended to describe the dummy with sufficient detail so that it is an objective measuring tool that produces consistent responses. NHTSA has codified numerous dummies that range in sex, size, age, and measurement capability. This includes dummies representing midsize adult males, small-stature adult females, infants, toddlers, and older children.

These dummies are meant to provide a range of body types in order to maximize data and test results that can assess injury and fatality risks in a range of crash outcomes. The 50th percentile male dummy currently defined in Part 572 for frontal impacts is the Hybrid III-50M, which NHTSA uses to test for compliance with the frontal crash test requirements in FMVSS No. 208, “Occupant crash protection” and to rate vehicles for NCAP. NHTSA added the HIII-50M to Part 572 in 1986.

This reflects a “bookend” approach to testing vehicles for crashworthiness, in which a range of occupant types, bookended by an average male and a small-stature female, is tested. NHTSA is currently supporting research to assess the possible benefits of developing new crash test dummies, such as a 50th percentile female crash test dummy.

NHTSA is continually researching and improving its test dummies and has been researching advanced test dummies since the implementation of the HIII-50M. An initial THOR-50M design was published in 2001. There are currently two different THOR dummies, the THOR-50M, and one under development that represents a small-statured adult female, the THOR 5th percentile adult female (THOR-05F). Although this proposal is limited to the THOR-50M, we anticipate publishing a rulemaking proposal in the near future to add the THOR-05F to Part 572.

The THOR-50M improves on the HIII-50M in a number of ways. It responds more like a human occupant in a crash and its advanced instrumentation enables it to more accurately measure the forces acting on the dummy. As a result, it is better able to predict the risk of injury to a human occupant. This should help vehicle designers develop and test improved occupant restraint systems (

e.g.,

advanced seat belts and air bags) as well as the types of novel vehicle seating configurations likely to be used in highly automated vehicles.

NHTSA has tentatively concluded that the THOR-50M is sufficiently biofidelic, exhibits repeatable and reproducible performance, and is sufficiently durable. As such, we believe that it would be suitable for use in regulatory compliance testing and is therefore suitable for incorporation into Part 572. NHTSA and others have already taken advantage of the THOR-50M's advanced capabilities. NHTSA, vehicle and restraint manufacturers, and vehicle safety researchers have used the THOR-50M to evaluate vehicle crashworthiness and develop occupant protection countermeasures for frontal and oblique crashes. The European New Car Assessment Programme (Euro NCAP) has officially adopted the THOR-50M and is currently rating vehicles using the dummy. Moreover, the Economic Commission for Europe is considering adopting the THOR-50M for use in frontal crash testing under its vehicle safety regulations.

NHTSA expects a variety of benefits from incorporating the THOR-50M into Part 572. The definition of the THOR-50M in Part 572 will enable its use in regulatory and consumer information programs, both within NHTSA and externally. NHTSA believes that the THOR-50M's enhancements will lead to more effective restraint system designs and more informative comparisons of the safety of different vehicles. Because of this—as well as the fact that manufacturers are already using the dummy—we believe vehicle manufacturers would choose to certify vehicles to FMVSS No. 208 using the THOR-50M if given the option. This would enable manufacturers to streamline testing by using the same dummy for research and development and to verify compliance. NHTSA anticipates issuing a proposal in the near future to amend FMVSS No. 208 to specify the THOR-50M as an alternative (at the vehicle manufacturer's option) to the HIII-50M test dummy for use in frontal crash compliance tests. There would be other benefits as well. For instance, NHTSA's test dummies are used in a range of applications beyond FMVSS compliance testing—such as NCAP testing, standards and regulations in other transportation modes, and research. Including the dummy design in Part 572 will help provide a suitable, standardized, and objective test tool for the safety community.

II. Background

This document proposes to amend 49 CFR part 572, Anthropomorphic Test Devices, to include an advanced test dummy representing a 50th percentile adult male, the Test Device for Human Occupant Restraint (THOR-50M).

The THOR-50M is a test dummy designed for use in frontal crash tests. It has several advanced capabilities and advantages over the Hybrid III 50th percentile male test dummy (HIII-50M) that is currently specified in Part 572 and used in frontal crash testing under FMVSS No. 208, “Occupant crash protection,” and the U.S. New Car Assessment Program (NCAP).

NHTSA plans to issue a proposal in the near future to amend FMVSS No. 208 to specify the THOR-50M as an alternative to the HIII-50M for use in frontal crash tests.

NHTSA has registered the term “THOR” as a trademark (U.S. Registration No. 5,104,395).

The HIII-50M is also specified for use in FMVSS No. 202a, Head Restraints, in an optional rear impact dynamic test.

FMVSS No. 208 THOR-50M Compliance Option (RIN 2127-AM21), Spring 2023 Unified Agenda of Regulatory and Deregulatory Actions; Department of Transportation, available at

https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21

This document proposes incorporating by reference in Part 572 a parts list, design drawings, qualification procedures, and procedures for assembly, disassembly, and inspection, to ensure that THOR-50M dummies are uniform in design, construction, and response. This section provides background on NHTSA's crash test dummies, the development of the THOR-50M, and its use in other jurisdictions, among other topics.

Overview of Use of Vehicle Crash Test Dummies

Anthropomorphic Test Devices (ATDs)—or crash test dummies—are complex instruments that serve as human surrogates in vehicle crash tests (among other types of tests

). Test dummies simulate the response of a human occupant in a crash and measure

the effects of the crash forces on the occupant. They are used to estimate the severity of the injuries that would have been experienced by a human occupant in a similar crash in the real world. Each type of test dummy is designed for use in specific types of crashes (frontal, side, etc.), and is instrumented with a wide array of sensors to measure the forces that would be relevant in the type of crash for which it is designed and to assess the potential for injury. The more closely a dummy represents how an actual human would respond, the more biofidelic the dummy is considered to be.

NHTSA also uses ATDs in sled tests (which simulate a vehicle crash by using a simplified test buck to represent a vehicle), and out-of-position air bag tests. ATDs are also used outside the vehicle safety context to measure human responses in a variety of other areas, such as aviation and aeronautics.

NHTSA and the vehicle safety community use crash test dummies in a variety of ways. NHTSA uses crash test dummies for vehicle compliance testing, safety ratings, and safety research. NHTSA's Federal Motor Vehicle Safety Standards establish mandatory minimum safety performance requirements for motor vehicles and motor vehicle equipment. Vehicles and equipment manufactured for sale in the United States must be certified to comply with all applicable FMVSSs. A number of the FMVSSs specify crash tests, using specified dummies, that the vehicle must be certified as passing.

NHTSA's vehicle safety compliance program selects vehicles (and equipment) for compliance testing every year; this includes crash testing vehicles to ensure that they comply with the performance requirements that are evaluated by means of crash tests. NHTSA's NCAP also evaluates vehicle performance in crash tests using dummies as part of its 5-Star Safety Ratings. Finally, NHTSA's vehicle safety research program uses crash test dummies to evaluate new vehicle safety countermeasures and develop new vehicle crash testing protocols. Dummies are also used outside of NHTSA by regulatory authorities in other countries and regions, for third-party ratings (such as Insurance Institute for Highway Safety ratings), and by industry and the vehicle safety community to measure performance and design safer vehicles.

The FMVSS specify the procedures NHTSA will use in compliance testing, including what dummies it will use for testing. Part 572 specifies the dummies. While manufacturers must exercise reasonable care in certifying that their products meet applicable standards, they are not required to follow the compliance test procedures set forth in a standard or use the dummy specified in Part 572.

See, e.g.,

38 FR 12934, 12935 (May 17, 1973) (“Manufacturers should understand that they are not required to test their products in any particular manner, as long as they exercise due care that their products will meet the requirements when tested by the NHTSA under the procedures specified in the standard.”).

The dummies NHTSA currently uses in FMVSS compliance testing and in NCAP are documented in 49 CFR part 572, Anthropomorphic Test Devices. Part 572 sets out detailed design information, including engineering drawings and procedures for assembly and inspection. These are all intended to describe the dummy with sufficient detail so that it produces consistent responses when it is tested under similar conditions in repeated tests at the same laboratory (repeatability) or between multiple dummies manufactured to the same specification used at different test laboratories (reproducibility).

FMVSS No. 208 Frontal Crash Tests Using a 50th Percentile Male Dummy

FMVSS No. 208, “Occupant crash protection,” specifies a variety of different requirements using crash test dummies. This includes frontal crash tests in which the vehicle is moving and tests that are performed with a stationary vehicle and are intended to help ensure that air bags do not harm small-stature occupants and children. The test dummies used in FMVSS No. 208 were designed to evaluate vehicle performance in frontal crashes and are fitted with a variety of instruments to measure the forces typically experienced by an occupant in a frontal crash.

The 50th percentile male dummy that is currently specified for use in FMVSS No. 208 is the Hybrid III-50M.

The HIII-50M has been specified in FMVSS No. 208 since 1986,

and replaced an even earlier dummy, the Hybrid II. FMVSS No. 208 also specifies tests using dummies representing a 5th percentile female, a 6-year-old, a 3-year-old, and an infant.

Other FMVSS specify different types of crash or sled tests that use different dummies. For example, FMVSS No. 214, Side Impact Protection, specifies two crash tests (simulating a side impact with a vehicle and a pole impact). This test uses two different side impact dummies.

Part 572, Subpart E.

51 FR 26688 (July 25, 1986) (final rule adding HIII-50M). The Hybrid III-50M was developed by General Motors and added to Part 572 and for use in FMVSS No. 208 in response to a petition for rulemaking from GM.

FMVSS No. 208 specifies two tests (both of which are crash tests) using the HIII-50M: a crash test in which the dummy is belted and the test vehicle, traveling up to 35 mph, impacts a rigid barrier at a ninety-degree angle or perpendicular;

and a crash test in which the dummy is unbelted and the test vehicle, traveling 20-25 mph, impacts a rigid barrier at an angle ranging from ± 30 degrees oblique from perpendicular.

NCAP also evaluates vehicle performance in a frontal crash test at 35 mph using a belted HIII-50M dummy.

S5.1.1(b)(2), S14.5.1(b).

S5.1.2(b), S14.5.2.

FMVSS No. 208 regulates vehicle performance in these crash tests by specifying injury criteria and associated injury assessment reference values (IARVs). Injury criteria and their respective risk functions relate instrumentation measurements to a predicted risk of human injury. Each IARV is a maximum value or threshold for a specific injury criterion that may not be exceeded when the vehicle is tested with the specified dummy under the specified test conditions and procedures. For example, FMVSS No. 208 specifies a head injury criterion, HIC

, with an IARV of 700. Thus, if NHTSA runs a compliance frontal crash test and the calculated HIC

value exceeds 700, this would be considered an apparent noncompliance. FMVSS No. 208 specifies the following injury criteria for the HIII-50M: a head injury criterion (HIC

);

a thoracic acceleration criterion;

a chest deflection criterion;

a criterion based on the maximum force transmitted axially through the upper leg (femur);

and three neck injury criteria.

S6.2(b).

S6.3.

S6.4.

S6.5.

S6.6.

Development of the THOR ATDs

NHTSA has continually conducted research into advancements in crash safety, including the development of advanced dummies.

The goal of this research has been to create ATDs that represent the responses of human occupants in modern vehicle environments with advanced restraint systems. This research has led to the development of the two Test Device for Human Occupant Restraint (THOR) ATDs, designed primarily for use in frontal and frontal oblique motor vehicle crash environments. There are currently two main implementations of the THOR design, both representing seated motor vehicle occupants: one representing a 50th percentile male and

one representing a 5th percentile female.

Haffner, M., Rangarajan, N., Artis, M., Beach, D., Eppinger, R., Shams, T., “Foundations and Elements of the NHTSA THOR Alpha ATD Design,” The 17th International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 458, 2001.

Development of THOR-50M

The initial design version of the THOR-50M, introduced in 2001, was the THOR Alpha.

The THOR Alpha, which integrated some components from the earlier prototype demonstrator known as the Trauma Assessment Device, introduced some of the features that exist in the current version of THOR-50M, including the multi-direction neck, human-like ribcage geometry and impact response, multi-point thorax and abdomen deflection measurement system, and instrumented lower extremities. NHTSA refined the THOR Alpha design and reintroduced it in 2005 as the THOR-NT,

which included updates to anthropometry, durability, usability, biofidelity, and fit and finish. In 2011, NHTSA, in coordination with the SAE International (SAE) THOR Evaluation Task Group, introduced a modification package (Mod Kit) intended to enhance the biofidelity, repeatability, durability, and usability of the THOR-NT.

After the introduction of the THOR Mod Kit, an upgrade to the Chalmers shoulder assembly that was developed through the European Union's THORAX project was integrated into the THOR-50M design.

The THOR-50M drawing package was then converted from the traditional measurement system to the metric system through soft conversion (where any non-metric measurements are mathematically converted to metric equivalents without changes to the physical dimensions). All fasteners were also replaced with the nearest metric equivalents. NHTSA made this integrated drawing package (with incremental improvements and corrections) publicly available online in 2015,

2016,

2020,

and 2023.

The version published in 2023 is referred to as the 2023 drawing package, which consists of two-dimensional drawings and a Parts list; this, together with the Procedures for Assembly, Disassembly, and Inspection (PADI), and qualification procedures, is referred to as the 2023 technical data package. (The version published in 2020 is referred to as the “2018 drawing package” or the “2018 technical data package.”) The version of THOR that is being proposed is the version defined in the 2023 technical data package. In 2019, NHTSA began publishing THOR-50M documentation in a new docket titled, “NHTSA Crashworthiness Research—THOR-50M Documentation.”

In addition to the documents that make up the 2018 and 2023 technical data packages, the docket folder includes the following: durability report; seating procedure; injury criteria; biofidelity report; Oblique Moving Deformable Barrier (OMDB) Repeatability and Reproducibility (R&R); and Qualification test R&R. This documentation is discussed further in Section III.B and in the relevant sections of this preamble.

Id.

Shams, T., Rangarajan, N., McDonald, J., Wang, Y., Platten, G., Spade, C., Pope, P., Haffner, M., “Development of THOR NT: Enhancement of THOR Alpha—the NHTSA Advanced Frontal Dummy,” The 19th International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 05-0455, 2005.

Ridella, S., Parent, D., “Modifications to Improve the Durability, Usability, and Biofidelity of the THOR-NT Dummy,” The 22nd International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 11-0312, 2011.

Lemmen, P., Been, B., Carroll, J., Hynd, D., Davidsson, J., Song, E., Lecuyer, E., “Development of an advanced frontal dummy thorax demonstrator,” Proceedings of the 2012 IRCOBI Conference, 2012.

National Highway Traffic Safety Administration (2015). Parts List and Drawings, THOR-M Advanced Frontal Crash Test Dummy, September 2015.

Regulations.gov

Docket ID NHTSA-2015-0119-0005,

available at: https://www.regulations.gov/document/NHTSA-2015-0119-0005

(NCAP docket).

National Highway Traffic Safety Administration (2016). Parts List and Drawings, THOR-50M Advanced Frontal Crash Test Dummy, August 2016,

available at: https://www.nhtsa.gov/es/document/thor-50m-drawing-package-august-2016.pdf

National Highway Traffic Safety Administration. Parts List and Drawings, THOR-50M Advanced Frontal Crash Test Dummy, August 2018.

Regulations.gov

Docket ID NHTSA-2019-0106-0002,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0002

National Highway Traffic Safety Administration. THOR 50th Percentile Male with Alternate Shoulders Frontal Crash Test Dummy Drawings, External Dimensions, and Mass Properties, THOR-50M Advanced Frontal Crash Test Dummy, August 2018.

Regulations.gov

Docket ID NHTSA-2019-0106-0013,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0013

Docket NHTSA-2019-0106.

These documents are located in the research docket, Docket No. NHTSA-2019-0106. NHTSA is not placing copies of these documents in the docket for this rulemaking action in order to avoid potential confusion from having identical documents docketed at different times in different dockets. Nevertheless, NHTSA intends these to be included as part of the rulemaking record for this rulemaking action. A memorandum explaining this is also being placed in the docket for this rulemaking.

Development of THOR-05F

NHTSA understands that the risk of injury in a crash can depend on the occupant's physical characteristics (

e.g.,

height, weight, bone density) and how they interact with the restraint system and vehicle environment. To that end, NHTSA has developed comprehensive research plans to address differences in crashworthiness safety testing and outcomes, including differences in injury risk. Human body modeling research efforts are underway to consider female and male occupants and vulnerable road users of various ages, shapes, and sizes. This includes continuing and accelerating research efforts to address differences in motor vehicle safety based on physical characteristics, including sex, and making data-driven decisions supported by the research outcomes. A series of efforts is specifically focused on female occupant crash safety, spanning field data analysis, tool development, demonstration, and application.

See

National Highway Traffic Safety Administration (2022). NHTSA Female Crash Safety Research Plan, November 2022.

Regulations.gov

Docket ID NHTSA-2022-0091-0002,

available at: https://www.regulations.gov/document/NHTSA-2022-0091-0002

As part of these efforts, NHTSA has been developing the THOR 5th percentile adult female frontal crash test dummy (THOR-05F). The THOR-05F represents a small adult female and has a seated height of 81.3 cm (32.0 in), approximate standing height of 151 cm (59.4 in), and weight of 49 kg (108.0 lbs). The THOR-05F has improved measurement capabilities over the Hybrid III-5F, which is specified in FMVSS No. 208 and documented in Part 572. The THOR-05F's instrumentation is similar to that of the THOR-50M. Improved designs resulting from the development of the THOR-50M related to the head, neck, thorax, and lower extremities have also been incorporated into the design of the THOR-05F. Currently, NHTSA is evaluating the THOR-05F's biofidelity and durability, developing design updates, injury criteria, and documentation, and assessing its utility in full-scale crash testing.

NHTSA anticipates completing the research and testing necessary to support a rulemaking for the THOR-05F

in 2023.

Possible test modes in which THOR-05F may be used include FMVSS No. 208 testing and NCAP frontal crash tests. NHTSA has placed documentation and research for the THOR-05F in an online docket and will continue adding additional research and information to this docket as it becomes available.

Part 572 THOR 5th Female Crash Test Dummy (RIN 2127-AM56), Spring 2023 Unified Agenda of Regulatory and Deregulatory Actions; Department of Transportation, available at

https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM56

. This rulemaking would amend 49 CFR part 572 by adding design and performance specifications for a new test dummy known as the THOR-05F.

See

Docket No. NHTSA-2019-0107, available at

regulations.gov

Innovative Features of the THOR-50M

Frontal crashes are the leading cause of injuries and fatalities in occupants of motor vehicle crashes on U.S. public roadways. The vehicle front is the initial point of impact in a majority of crashes in the U.S. In 2021, 15,570 occupants of passenger cars or light trucks died, and 1,144,169 were injured, in frontal crashes.

This suggests that even though occupant protection systems have improved over the years and saved many lives,

improvements to occupant protection in frontal crashes still need to be made.

Data Sources: Fatality Analysis Reporting System (FARS): 2017-2020 Final File and 2021 Annual Report File (ARF); Report Generated: Wednesday, June 28, 2023 (12:48:52 p.m.); VERSION 5.6, RELEASED MAY 19, 2023

Charles J. Kahane, Lives Saved by Vehicle Safety Technologies and Associated Federal Motor Vehicle Safety Standards, 1960 to 2012—Passenger Cars and LTVs—With Reviews of 26 FMVSS and the Effectiveness of Their Associated Safety Technologies in Reducing Fatalities, Injuries, and Crashes. 89 DOT HS 812 069 at 89, Department of Transportation, National Highway Traffic Safety Administration (2015).

The THOR-50M is designed to better evaluate the effectiveness of modern vehicle restraint systems and address the types of injuries that continue to occur. These improvements include the following:

Improved biofidelity.

Biofidelity is a measure of how well a dummy replicates the response of a human. The THOR-50M was designed with advanced features that enable it to have improved biofidelity compared to the HIII-50M. The dummy's head includes a deformable facial insert that emulates human response to impact. The components in the neck representing bone and ligament structure are separate from those representing muscular structure, improving both kinematic response and injury prediction. The thorax simulates the shape and impact response of the human rib cage. The spine incorporates flexible joints in the thoracic and lumbar spine, allowing dynamic spine flexion as well as static adjustment in the neck and lumbar spine to accommodate seating in various postures. The upper leg has a compressive element in the femur and the lower leg has a compressive element in the tibia and an Achilles tendon load path to achieve human-like impact response. The biofidelity of the THOR-50M has been assessed in a wide array of both component and full-body test conditions for which human response is known and was found to be both qualitatively and quantitatively congruent with human response corridors.

Improved instrumentation.

The THOR-50M has both improved and additional instrumentation compared to the HIII-50M. The thorax instrumentation measures the three-dimensional deformation of the rib cage at four locations. The abdomen is also designed with a multi-point measurement system that monitors three-dimensional deformation of the abdomen at two locations. The upper leg includes an acetabulum load cell in the pelvis to measure load transfer from the femur to the hip. The lower leg has extensive instrumentation to support injury risk calculation.

Improved injury prediction.

The biofidelity of the THOR-50M, combined with its extensive instrumentation, provides an enhanced capability to measure expected human response and predict injury. Injury criteria and injury risk functions, which relate instrumentation measurements to a predicted risk of human injury, have been developed for the head, neck, chest, abdomen, pelvis, upper leg, and lower leg of the THOR-50M.

These include injury criteria analogous to those currently specified for the HIII-50M in FMVSS No. 208 as well as injury criteria that are not currently specified for the HIII-50M in FMVSS No. 208. We believe this enhanced injury prediction capability will translate into restraint system designs that have the potential to enhance occupant protection. NHTSA and others, including vehicle manufacturers, have already taken advantage of these capabilities in the research arena.

Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E., Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD.

Regulations.gov

Docket ID NHTSA-2019-0106-0008,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0008.

Improved evaluation of vehicle performance.

These enhancements allow the THOR-50M to better differentiate the performance of different vehicles and restraint systems. The more sophisticated measurement capabilities of an advanced ATD are better suited to develop and test more sophisticated and highly tunable contemporary restraint systems with features such as multi-stage air bags and force-limiting/pretensioning seat belts. Motor vehicle manufacturers and restraint suppliers have already used the THOR-50M to evaluate vehicle crashworthiness and develop occupant protection countermeasures. Numerous conference and journal articles describing the use of the THOR-50M have been published. For example, in a study examining the performance of different restraint systems in frontal impact sled tests using both the THOR-50M and HIII-50M, the THOR-50M was found to be more sensitive to the restraint conditions, as it was able to differentiate between both crash severity and restraint performance.

Another study investigated a novel air bag system with three inflated chambers with a connected sail panel to promote earlier engagement with the occupant and prevent lateral motion and head rotation; sled testing using the THOR-50M demonstrated a reduction in brain injury risk due to head angular velocity, as quantified using the Brain Injury Criterion (BrIC).

Other studies have also implemented the THOR-50M to assess and develop restraint systems.

Sunnevång, C., Hynd, D., Carroll, J., Dahlgren, M., “Comparison of the THORAX Demonstrator and HIII Sensitivity to Crash Severity and Occupant Restraint Variation,” Proceedings of the 2014 IRCOBI Conference, Paper No. IRC-14-42, 2014.

Hardesty, J. (2021). Next-Generation Passenger Airbag. SAE Government-Industry Digital Summit (oral only).

See also, e.g.,

Hu, J., Reed, M. P., Rupp, J. D., Fischer, K., Lange, P., & Adler, A. (2017). Optimizing seat belt and airbag designs for rear seat occupant protection in frontal crashes (No. 2017-22-0004). SAE Technical Paper; Eggers, A., Eickhoff, B., Dobberstein, J., Zellmer, H., Adolph, T. (2014). Effects of Variations in Belt Geometry, Double Pretensioning and Adaptive Load Limiting on Advanced Chest Measurements of THOR and Hybrid III. Proceedings of the 2014 IRCOBI Conference, Paper No. IRC-14-40; Hu, J., Fischer, K., Schroeder, A., Boyle, K., Adler, A., & Reed, M. (2019, October). Development of oblique restraint countermeasures (Report No. DOT HS 812 814). Washington, DC: National Highway Traffic Safety Administration. Available at:

https://rosap.ntl.bts.gov/view/dot/44143.

Adoption of the THOR-50M in Europe

In 2013, the European Commission (EC) issued a final report detailing the need for a new crash test dummy as a means to implement regulatory requirements for new vehicle safety technologies, particularly those technologies that reduce thorax injuries in frontal crashes.

At the time, the

THOR-50M was envisioned as the best evaluation tool for this purpose. In 2015, United Nations Economic Commission for Europe (UNECE) Regulation No. 137 (R137) went into effect. R137 specifies a 50 km/h, full-width rigid barrier frontal impact test with driver and passenger HIII-50M and HIII-5F dummies respectively. One objective of the regulation was to encourage better restraint systems across a wider range of collision severities.

European Commission, Seventh Framework Programme, THORAX Project Final Report,

Thoracic injury assessment for improved vehicle safety, 1/7/2013.

Seidl, M., Edwards, M., Barrow, A., Hynd, D., & Broertjes, P. (2017). The Expected Impact of UN Regulation No. 137 Tests on European Cars and Suggested Test Protocol Modifications to Maximise Benefits. In 25th International Technical Conference on the Enhanced Safety of Vehicles (ESV).

In 2017, an ECE-funded study found that the R137 condition and dummy diversity were not sufficiently different to existing UN Regulation No. 94 (R94) to force improvements in restraint systems. R94 involves a 56 km/h frontal offset test which also prescribes the HIII-50M in the driver and right front seat. To deliver the expected benefits, the 2017 final report recommended implementation of the THOR-50M in R137 as a replacement for the HIII-50M.

The THOR-50M was recognized as being more biofidelic in its representation of thoracic response and prediction of thorax injuries, which are the key serious and fatal injury types in full-width collisions targeted by R137.

Seidl M, Hynd D, McCarthy M, Martin P, Hunt R, Mohan S, Krishnamurthy V and O'Connell S: TRL Ltd. (2017). In depth cost-effectiveness analysis of the identified measures and features regarding the way forward for EU vehicle safety, Final Report, ISBN 978-92-79-68704-4, European Commission, 08-31-2017.

In 2018, the EC published a report on the cost-effectiveness and the number of future injuries and fatalities that could be prevented at a European level for different sets of vehicle safety measures.

Several new sets of safety measures were considered for mandatory implementation in new vehicles starting from 2022. This included the introduction of the THOR-50M into R137. The THOR-50M was considered for inclusion in a program titled “Full-width Frontal Occupant Protection with THOR (FFW-THO),” which would lower injury criteria thresholds to encourage implementation of adaptive restraints. It was envisioned that the implementation of the THOR-50M would result in an initial cost of 16 Euros per vehicle, for vehicles that currently comply with UN Regulation No. 137 with Hybrid III ATDs but not with THOR-50M ATDs. It was estimated that vehicles that comply with FFW-THO would provide a 6% increase in effectiveness in protecting against serious injuries compared to vehicles that comply with R137 alone.

Seidl, M., Khatry, R., Carroll, J., Hynd, D., Wallbank, C., Kent, J. (2018) Cost-effectiveness analysis of Policy Options for the mandatory implementation of different sets of vehicle safety measures—Review of the General Safety and Pedestrian Safety Regulations, Technical Annex to GSR2 report SI2.733025.

In 2019, the EC presented work priorities to WP.29

for 2019-2021 for UNECE activities. An amendment to introduce the THOR-50M into R137 was included. The target date for a WP.29 vote was listed as Q4/2021.

In 2020, Japan and the EC jointly initiated discussions within WP.29 to establish a priority for the new task. In preparation for an eventual adoption into R137, the E.C. commissioned TRL (Transport Research Laboratory, UK)

to conduct a survey of various stakeholders on the readiness of the THOR-50M. ATD manufacturers, crash test laboratories, and crash safety research laboratories were consulted. The results of the survey are contained within Annex 7 of a broader report on general safety regulations, published by the E.C. in 2021.

In the E.C. report, there are a number of recommendations based on stakeholder feedback. They include revisions to the dummy design and qualification procedures that may be needed prior to adopting THOR-50M into M.R. 1

and R137. Most stakeholders recommended the formation of either an Informal Working Group or a Technical Evaluation Group under the umbrella of UNECE WP.29 to co-ordinate this activity. As of May 2023, a WP.29 working group has yet to be established and timelines for amendments to R137 and M.R. 1 are undetermined. The areas for further investigation identified in Annex 7 are discussed in this NPRM.

This was a thrice-annual briefing on the regulatory status within the various working parties under WP.29's World Forum for Harmonization of Vehicle Regulations, including the status of R137 under the Working Party for Passive Safety (GRSP).

WP.29-177-18, 177th WP.29, 12-15 March 2019, EU Work priorities for 2019-2021 for UNECE activities.

TRL serves as an independent advisory to the E.C. TRL's report was performed under contract with the European Commission (E.C.), who sought to update the General Safety Regulation for Europe to include new and developing technologies with the aim of reducing Europe's annual road fatalities. The report reflects TRL's recommendations for consideration by the E.C.

General Safety Regulation: Technical study to assess and develop performance requirements and test protocols for various measures implementing the new General Safety Regulation, for accident avoidance and vehicle occupant, pedestrian and cyclist protection in case of collisions, Final Report, March 2021, Publications Office of the EU (europa.eu)), ISBN 978-92-76-08556-0, DOI 10.2873/499942, Catalogue number, ET-04-19-467-EN-N.

https://op.europa.eu/en/publication-detail/-/publication/6987b729-a313-11eb-9585-01aa75ed71a1/language-en/format-PDF/source-217672351

(last accessed 5/25/2023).

Mutual Resolution No. 1 (M.R.1) of the 1958 and the 1998 Agreements. Concerning the description and performance of test tools and devices necessary for the assessment of compliance of wheeled vehicles, equipment and parts according to the technical prescriptions specified in Regulations and global technical regulations, ECE/TRANS/WP.29/1101, 10 January 2013.

Although the ECE has not yet officially adopted the THOR-50M, the European New Car Assessment Programme (Euro NCAP) has been rating vehicles using the dummy. Euro NCAP has implemented a moving progressive deformable barrier (MPDB) frontal impact testing protocol with a THOR-50M in the driver's seat.

The THOR-50M used by Euro NCAP is specified in Technical Bulletin 026 (TB026)

“THOR Specification and Certification.”TB026 explicitly adopts—with some variations—NHTSA's 2018 technical data package (

i.e.,

the 2018 drawing package,

qualification procedures,

and PADI

). The variations to the 2018 technical data package are relatively limited. For example, TB026 specifies an onboard (in-dummy) data acquisition system and a variation to the adjustable spine to facilitate data acquisition system (DAS) installation; minor deviations in the shoulder assembly; and the use of the HIII-50M lower legs. These modifications are discussed in more detail in the relevant sections of the preamble and are summarized in Section IX, Consideration of alternatives. NHTSA's understanding is that no regulatory authorities or third-party vehicle rating programs other than Euro NCAP currently specify the THOR-50M for use in vehicle crash tests.

European New Car Assessment Programme (2022). MPDB Frontal Impact Testing Protocol, Version 1.1.3, available at:

https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/.

European New Car Assessment Programme (2023). THOR Specification and Certification, Version 1.3,

available at: https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/.

§ 1.1.

§ 2.1.

§ 3.1.

Motor vehicle and equipment manufacturers' interest in the design and operation of the THOR-50M has been heightened since the dummy was introduced into Euro NCAP and plans for R137 were announced. Discussions are taking place within International Standards Organization (ISO) Technical Committee 22 (Road Vehicles), Sub-Committee 36 (Safety and impact testing), Working Group 5 (Anthropomorphic test devices) for

modifications suggested by manufacturers. With no defined European entity to maintain configuration control, ISO has enlisted Humanetics Innovative Solutions, Inc. (Humanetics) to investigate its change recommendations directly. In particular, discussions have taken place regarding modifications to the shoulder pad and rib guide. These modifications are discussed in the relevant sections of the NPRM.

Need for This Rulemaking

NHTSA expects a variety of benefits from incorporating the THOR-50M in Part 572. The THOR-50M is an advanced dummy with many advantages over existing dummies with respect to biofidelity, instrumentation, and injury prediction. NHTSA believes that the THOR-50M's enhancements will lead to more effective restraint system designs and more informative comparisons of the safety of different vehicles. Euro NCAP has adopted it, the ECE is considering it for use in R137, and it is likely being used by vehicle and restraint manufacturers for testing, research, and development. Therefore, we believe vehicle manufacturers would choose to certify new vehicles using the THOR-50M if given the option, because this would enable manufacturers to streamline testing by using the same dummy for research and development and to verify compliance and vehicle ratings. NHTSA is therefore also considering a proposal to amend FMVSS No. 208 to give vehicle manufacturers the option of selecting the THOR-50M for use in belted and unbelted crash testing instead of the HIII-50M.

FMVSS No. 208 THOR-50M Compliance Option (RIN 2127-AM21), Fall 2023 Unified Agenda of Regulatory and Deregulatory Actions; Department of Transportation, available at

https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21.

This rulemaking would propose injury assessment reference values for the THOR-50M comparable to the IARVs currently specified for the HIII-50M.

There would be other benefits as well. For instance, the THOR-50M is well-suited for the types of new seating configurations brought on by vehicles with Automated Driving Systems (ADS). NHTSA is developing an adaptation of the THOR-50M that is better suited for reclined postures which may be prevalent among ADS occupants.

NHTSA's test dummies are also used in a range of applications beyond FMVSS compliance testing—such as NCAP testing, standards and regulations in other transportation modes, and research. While the purpose of Part 572 is to describe the anthropomorphic test devices that are to be used for compliance testing of motor vehicles and motor vehicle equipment with motor vehicle safety standards,

it also serves as a definition of the ATD for other purposes, such as consumer information crash testing, standards and regulations in other transportation modes, and research. As such, it would be to the benefit of government, academia, and the multi-modal transportation industry to include a definition of the THOR-50M ATD in Part 572.

Forman, J., Caudillo-Huerta, A., McMahon, J., Panzer, M., Marshall, W., Winter, D., Dyer, M., Lemmen, P. (2021). Modifications to the THOR-50M for Improved Usability in Reclined Postures—Update and Preliminary Findings. 2021 SAE Government-Industry Digital Summit,

available at: https://www.nhtsa.gov/node/103691.

The adaptation to the THOR-50M design for use in reclined seating environments is outside of the scope of this Part 572 NPRM.

49 CFR 572.1.

For example, American Public Transportation Association standard APTA PR-CS-S-018-13 Rev. 1 describes the use of a THOR ATD in the testing of fixed workstation tables in passenger rail cars. American Public Transportation Association. (2015, October). Fixed Workstation Tables in Passenger Rail Cars. PR-CS-S-018-13, Rev. 1. Washington, DC,

available at: https://www.apta.com/wp-content/uploads/Standards_Documents/APTA-PR-CS-S-018-13-Rev-1.pdf.

III. Design, Construction, and Instrumentation

In this section we discuss the anthropometry, design, construction, and instrumentation of the THOR-50M.

A. Anthropometry

The THOR-50M is a physical model of a 50th percentile male motor vehicle occupant. It is intended for use in the development and evaluation of vehicle safety countermeasures and vehicle safety performance in frontal crash tests. To ensure that the dummy responds in a human-like manner in a vehicle crash environment, it is necessary that the size and shape of the dummy, referred to as anthropometry, provide an accurate representation of a mid-sized male. The anthropometry of the THOR-50M is based on a study by the University of Michigan Transportation Research Institute that documented the anthropometry of a mid-sized (50th percentile in stature and weight) male occupant in an automotive seating posture (AMVO study).

56 57

This study defines an average male as 76.57 kg (168.8 lb) in weight with a standing height of 175.1 cm (68.9 in). The AMVO study is currently internationally accepted as the standard anthropometry for the 50th percentile male ATD. The THOR-50M has a mass of 77.37 kg (170.6 lb) and a seated height of 101.8 cm (40.2 in). The standing height of the ATD cannot be measured since the pelvis does not allow a full standing posture; however, since it was developed using the AMVO body segment geometry and seated anthropometry, it is assumed that the stature of the THOR-50M is also 175.1 cm.

Schneider, L.W., Robbins, D.H., Pflug, M.A., Snyder, R. G., “Development of Anthropometrically Based Design Specifications for an Advanced Adult Anthropomorphic Dummy Family; Volume 1-Procedures, Summary Findings and Appendices,” U.S. Department of Transportation, DOT-HS-806-715, 1985.

Robbins, D.H., “Development of Anthropometrically Based Design Specifications for an Advanced Adult Anthropomorphic Dummy Family; Volume 2-Anthropometric Specifications for mid-Sized Male Dummy; Volume 3- Anthropometric Specifications for Small Female and Large Male Dummies,” U.S. Department of Transportation, DOT-HS-806-716 & 717, 1985.

The THOR-50M is consistent with the AMVO anthropometry. NHTSA compared the dimensions of a representative dummy (S/N 9798) with the AMVO target dimensions (Table 1).

The AMVO procedure originally used to collect measurements from volunteers was adapted to collect the same or similar measurements on the THOR-50M.

Most of these measurements were taken with the THOR-50M seated on the AMVO bench, which has an angled seat and backrest. One adaptation was necessary to collect leg measurements on the AMVO bench: the THOR-50M has an integrated molded shoe that cannot be separated from its foot, while the AMVO data were collected on barefoot volunteers. To remedy this situation, the THOR-50M measurements were recorded after removing the entire molded shoe assembly and positioning the center of the ankle joint at the same location as the AMVO ankle landmark. Another adaptation was that four of the measurements were collected with the THOR-50M seated on a 90-degree bench, as specified on drawing 472-0000, Sheet 4. NHTSA also compared

the body segment masses specified in the proposed THOR drawing package (472-0000, Sheet 5) with the AMVO body segment masses (Table 2), and the masses were also consistent.

A THOR-50M unit is a collection of serialized parts that can be swapped out with other dummies, so is not considered a “serialized” dummy. Indeed, many of the subassemblies that were part of S/N 9798 when NHTSA took these measurements were subsequently swapped out of the dummy.

See

Section VII.A.

These AMVO measurements were collected as an assessment of anthropometry; it is understood that there is variation in initial position and measurement methodology that prevents the use of such measurements as a repeatable dimensional assessment. In practice, a simplified set of dimensional requirements are put in place as a check for overall part fit, tolerance stack, and to ensure that the dummy is assembled correctly. These requirements are specified on drawing 472-0000, Sheet 4, and are collected following the “Procedures for Measuring External Dimensions” section of the PADI.

Table 1—THOR-50M Anthropometry Compared to AMVO

Dimensions

(all measurements in centimeters)

AMVO target

(Robbins et al 1983)

THOR-50M

S/N 9798

Height of top of head to floor

100.3

101.8

Height of shoulder to floor

72.1

74.2

H-point to knee joint distance (note 1)

43.2

42.3

Buttock to knee end distance (note 2)

59.3

62.0

Height of knee from floor

45.3

47.0

Head circumference

57.1

58.7

Head top-chin distance

19.7

22.9

Head breadth

15.8

15.3

Chest circumference

101.1

95.5

Chest breadth

34.9

30.9

Chest depth (note 3)

22.7

22.4

Abdomen circumference

91.3

99.0

Abdomen breadth

32.5

Abdomen depth (note 2)

26.9

29.8

Pelvis breadth

38.5

38.8

Thigh max circumference

57.9

56.8

Thigh max breadth

19.4

17.1

Mid thigh circumference

50.4

56.0

Mid thigh breadth

15.5

17.8

Calf circumference

37.3

37.5

Calf breadth

11.0

9.1

Calf depth

11.8

11.9

THOR-50M specified on 472-0000, Sh. 4, measurement F (Knee Pivot to Hip Pivot) as seated upright on a 90-degree bench.

THOR-50M and AMVO measured as seated upright on a 90-degree bench.

THOR-50M specified on 472-0000, Sh. 4, measurement I (Rib #3 depth) as seated upright on a 90-degree bench without jacket installed.

Table 2—THOR-50M Body Segment Masses Compared to AMVO

Body segment masses

(all measurements in kilograms)

AMVO target

(Robbins et al 1983)

THOR-50M specification *

Head

4.137

** (4.55)

4.501

Neck

0.965

2.363

Thorax

23.763

23.517

Lower Abdomen

2.365

2.664

Pelvis

11.414

15.229

Upper Arm, Left or Right

1.769

1.701

Lower Arm with Hand, Left or Right

2.022

2.227

Upper Leg, Left or Right

8.614

5.618

Lower Legs, Left or Right

3.587

3.396

Feet, Left or Right including shoe

*** 1.551

1.604

Total Weight

76.562

77.366

* Listed on Drawing No. 472-0000, Sh. 5.

** Mass reported in Melvin JW, Weber, K. “Task B Final Report: Review of Biomechanical Impact Response and Injury in the Automotive Environment,” U.S. Department of Transportation, DOT-HS-807-042, 1985. The AMVO target is believed to be too low.

*** This adds the mass of a size 11 Oxford shoe (0.57 kg) specified for use in FMVSS No. 208 for the HIII-50M) to the AMVO specification of 0.981 kg so as to be comparable to the THOR's foot-within-a-molded-shoe mass.

B. Technical Data Package

The construction of the THOR-50M is similar to other ATDs currently defined in Part 572, with a metallic frame largely covered in urethane and/or vinyl representing flesh; body segments connected by translational and rotational joints; and deformable rubber or foam elements to prevent hard contact between metallic surfaces and to provide human-like impact response. The kinematic and dynamic biomechanical performance requirements of the THOR-50M were developed based on post-mortem human subject (PMHS) and volunteer response data, described in Section IV, Biofidelity.

The THOR-50M that we are proposing in this NPRM is the version defined in the 2023 technical data package (consisting of two-dimensional engineering drawings and a Parts list; procedures for assembly, disassembly, and inspection (PADI); and qualification procedures). The 2023 technical data package also includes an addendum with the drawings and drawing/parts list for an alternate configuration with an in-dummy data acquisition system, as discussed in Section III.N, Data Acquisition System. It is anticipated that, upon finalization of this proposal,

the in-dummy DAS drawings will be fully integrated within the relevant technical data package components. The technical data package is summarized in Table 3. For these documents, the NPRM cites to the document location in the research docket. NHTSA is not placing copies of these documents in the rulemaking docket, in order to avoid potential confusion from having identical documents docketed at different times in different dockets. However, NHTSA intends these to be included as part of the rulemaking record. A memo explaining this is also being included in the rulemaking docket. In addition, as noted in the background section, NHTSA began publishing the technical data package to its website starting in 2015. The 2023 technical data package updates the 2018 technical data package. These updates were made to address typographical errors, improve clarity, and add alternative design elements. Table 4 summarizes these updates.

Table 3—THOR-50M Technical Data Package

Title

Link

THOR 50th Percentile Male with Alternate Shoulders Frontal Crash Test Dummy Drawings, External Dimensions, and Mass Properties

https://www.regulations.gov/document/NHTSA-2019-0106-0013.

*THOR-50M DAS Integration Kit Drawings, April 2023

https://www.regulations.gov/document/NHTSA-2019-0106-0019.

*Parts List, THOR-50M DAS Integration Kit, April 2023

https://www.regulations.gov/document/NHTSA-2019-0106-0018.

Parts List, THOR 50th Percentile Male Frontal Crash Test Dummy with Alternate Shoulders

https://www.regulations.gov/document/NHTSA-2019-0106-0015.

THOR 50th Percentile Male (THOR-50M): Procedures for Assembly, Disassembly, and Inspection (PADI): June 2023

https://www.regulations.gov/document/NHTSA-2019-0106-0017.

THOR 50th Percentile Male (THOR-50M) Qualification Procedures and Requirements, April 2023

https://www.regulations.gov/document/NHTSA-2019-0106-0010.

* The DAS Integration Kit drawings and drawing/parts list would not themselves be incorporated by reference into Part 572. It is anticipated that, upon finalization of this proposal, these documents will be fully integrated within the relevant technical data package components.

Table 4—Summary of Updates Made in the 2023 THOR-50M Technical Data Package

Technical Data Package Element

Revisions in 2023 Version

Drawing Package

Includes drawings for alternate shoulder, removal of notes suggesting that qualification specifications supersede drawing specifications, and changes to correct typographical drawing errors. Complete change log found in “THOR-50th Percentile Male with Alternate Shoulders (THOR-50M w/ALT. SHOULDERS) Drawing Revisions”.

PADI

Minor typographical changes; complete change log found in Section 20 of “THOR 50th Percentile Male (THOR-50M) Procedures for Assembly, Disassembly, and Inspection (PADI)”.

Qualification Procedures

Revised upper leg qualification test mode, adjusted language to be more prescriptive, removed unit conversions, and corrected typographical errors. Complete change log found in Appendix B of “THOR 50th Percentile Male (THOR-50M) Qualification Procedures and Requirements, April 2023”.

Below

we briefly discuss several aspects of the technical data package in more detail.

See Table 5.

Engineering Drawings and Parts List

The engineering drawings and parts list specify the configuration of the THOR-50M. Included in the drawings are the required dimensions and tolerances, material properties, and component or material testing requirements and associated specifications. In a few instances, the drawings specify quasi-static tests and/or performance requirements for individual parts (such as a compression or flexion test for a molded part or subassembly); however, passing a specified performance (or qualification) test is not an alternate criterion for accepting a part that deviates from the drawing specifications.

All instruments are specified by corresponding SA572-xxx drawings.

SA drawings are included for associated mounts and hardware that are not otherwise needed when the dummy is configured with a corresponding structural replacement. Brand name call-outs are only used for parts and materials that have widespread availability and are used for a wide variety of non-ATD applications. It includes materials widely identified by their tradenames, such as Teflon, Acetal, Lexan, and Nitinol. Call-outs are also used for bonding agents, fasteners, and other items that are also widely available for non-ATD applications.

In the drawings which were part of the August 2018 technical data package, several notes state that “qualification takes precedence over design.” These notes were unintentionally carried over from earlier drawing versions used during THOR-50M development, and have since been removed. These are reflected in the proposed 2023 technical data package. In cases where some flexibility is allowed in order to meet the qualification specification, a “REF.” prefix is added to specific dimensions or material specifications.

This convention is used for all instruments on all Part 572 dummies. SA572 simply indicates that it is an instrument, and Sxx is the next-in-line number assigned by NHTSA to the instrument. Some load cells (and part numbers) are used on different Part 572 subpart dummies. For THOR, this applies to SA572-S4 (accelerometer) which is used on many other dummies.

In some instances, the drawing package permits two different part or instrumentation configurations that are both fully specified. For example, the head accelerometer mounting plate assembly drawing (472-1200) calls out three different angular rate sensors (SA572-S56, SA572-S57, or SA572-S58) which may be desired by the end user depending on the implementation of the ATD.

In the sections below on specific body regions we discuss the proposed as well as alternate designs and instrumentations that are not included in the proposed specifications but which we are considering specifying in the final rule and on which we are seeking comment. If NHTSA were to use the dummy for FMVSS compliance testing, NHTSA could test with any alternative configurations at its own discretion. Thus, the IARVs would have

to be met using a dummy with any permissible configuration. Manufacturers are not required to test their products in any particular manner, as long as they exercise due care that their products will meet the requirements when tested by NHTSA under the procedures specified in the standard, including the relevant dummy specified in Part 572.

However, a manufacturer would not be able to claim that a vehicle fully complies with a standard if it meets the standard's requirements in only one of the dummy's configurations, but not the other.

Similar situations exist with currently federalized ATDs, such as the HIII-10C, where either a chest slider pot or an IR-TRACC is permissible.

See, e.g.,

In addition to the engineering drawings that would be incorporated by reference, we are also providing supplemental documentation on the form and function of the THOR-50M. These reference materials are summarized in Table 5. These files would not be incorporated by reference in Part 572 and would therefore not be part of the THOR-50M specification. Instead, they are intended only for reference purposes (

e.g.,

to facilitate fabrication and inspection of parts with intricate geometries).

Table 5—THOR-50M Design Reference Documentation

Title

Link

THOR-50M Drawing Package—2D AutoCAD Jan 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20with%20Alternate%20Shoulders%20Jan%202023-AutoCAD%20DWG%20Files.zip.

THOR-50M Drawing Package—3D Inventor Format Jan 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20with%20Alternate%20Shoulders%20Jan%202023-Inventor%20Files.zip.

THOR-50M Drawing Package—3D STEP Format Jan 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20DAS%20Integration%20Kit-3D%20STEP%20Files_April%202023.zip.

THOR 50th Percentile Male with Alternate Shoulders Drawing Revisions, Jan 2023

https://www.regulations.gov/document/NHTSA-2019-0106-0014.

THOR-50M DAS Integration Kit—2D AutoCAD, April 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20DAS%20Integration%20Kit-AutoCAD%20DWG%20Files_April%202023.zip.

THOR-50M DAS Integration Kit—3D STEP Format, April 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20DAS%20Integration%20Kit-3D%20STEP%20Files_April%202023.zip.

THOR-50M DAS Integration Kit—Inventor Format, April 2023

https://static.nhtsa.gov/nhtsa/downloads/THOR_50M_Drawing_Package/NPRM/THOR-50M%20DAS%20Integration%20Kit-Inventor%20Files_April%202023.zip.

The THOR-50M used by Euro NCAP is specified in Technical Bulletin 026, “THOR Specification and Certification.”

TB026 explicitly adopts—with some deviations—the 2018 drawing package.

These deviations in TB026 include specification of an onboard (in-dummy) data acquisition system and a variation to the adjustable spine to facilitate DAS installation; minor deviations in the shoulder assembly; and the use of the HIII-50M lower legs. These modifications are discussed in more detail in the relevant sections of the preamble, and are summarized in Section IX, Consideration of alternatives. Euro NCAP TB026 specifies the 2018 drawing package, while this proposal specifies the 2023 drawing package. However, given the differences described in Table 4 above, this deviation is likely to be inconsequential. The deviations TB026 makes to the 2018 drawing package are not accompanied by engineering drawings, which may tend to lessen the dummy's overall objectivity. Objectivity is a statutory necessity for ATDs in Part 572. While the lack of accompanying drawings for these deviations may be adequate for the Euro NCAP rating program, it could lead to a future population of THOR-50M units that are sufficiently non-uniform as to render them unsuited for FMVSS applications.

European New Car Assessment Programme (2023). THOR Specification and Certification, Version 1.3,

available at: https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/.

§ 1.1.

PADI

The PADI provides step-by-step procedures on how to properly assemble the dummy. This includes instructions on part alignment, torque settings, wire routings, and other adjustments that are not otherwise described in the engineering drawings. The PADI provides explicit installation instructions for all instruments. Euro NCAP TB026 specifies the 2018 PADI,

while this proposal specifies the 2023 PADI. However, the differences between the 2018 PADI and 2023 PADI are primarily corrections to typographic errors, so this deviation is likely to be inconsequential. In some instances, the drawing package permits two different part or instrumentation configurations that are (or will be in the final rule) both fully specified (for example, the IR-TRACC and the S-Track for the chest instrumentation). The proposed PADI does not currently contain installation instructions for the optional parts (

e.g.

alternate shoulder) or instrumentation (

e.g.,

the S-Track). However, where multiple optional configurations are permitted and installation differences are non-trivial, NHTSA anticipates supplementing the PADI with such instructions in the final rule.

§ 3.1.

Qualification Procedures

The qualification procedures describe a series of impact tests performed on a fully assembled dummy or sub-assembly. NHTSA has established numeric bounds or acceptance intervals for the ATD responses in these tests. The qualification procedures are discussed in Section V.

Summary

NHTSA believes that the technical data package adequately describes and would ensure the uniformity of the dummy. Upon finalization of this proposal, a new subpart for the THOR-50M would be added to Part 572, and the technical data package documents would be incorporated by reference.

NHTSA seeks comment on whether the dummy is sufficiently specified to ensure that dummies are uniform such that they will provide repeatable and reproducible measurements. We also seek comment on whether it would be useful to end-users of the dummy if NHTSA created a list of suppliers used by NHTSA to obtain various parts and instrumentation, and/or general specifications or operating characteristics of a part (as provided by a manufacturer's specification sheet). Such documentation would not be incorporated into Part 572 but would be provided as a reference aid for users and could be periodically updated by NHTSA.

C. Head and Face

The head of the THOR-50M is primarily constructed of a cast aluminum skull covered in a urethane head skin. It includes two features not seen on the HIII-50M: spring towers and a featureless face. The spring towers are integral to the response of the head/neck system, as they are the mounting location of the cables that represent the musculature of the neck (described further in the following section). The head is equipped with three uniaxial accelerometers and three angular rate sensors at the head center of gravity (CG) to measure translational acceleration and angular velocity, respectively. The head also includes a biaxial tilt sensor which measures the quasi-static orientation of the head for pre-test positioning purposes.

The face is constructed of an open-cell urethane foam sandwiched between the head skin and the face load distribution plates. The featureless face allows for more repeatable and reproducible interactions with potential contact surfaces and meets enhanced biomechanical response requirements which have not been implemented on any existing ATDs. Additionally, the face can be configured with five uniaxial load cells: left and right eye, left and right cheek, and chin.

These load cells have not been used in any tests currently available in NHTSA's Vehicle or Biomechanics databases, and are typically replaced with structural replacements during testing. While the THOR-50M Qualification Procedure does include a face impact test which would exercise the face load cells if installed, there are currently no qualification specifications on face load cell forces.

D. Neck

The neck of the THOR-50M is visibly and functionally different than the ATDs currently defined in Part 572. While typical ATD designs use only a pin joint between the base of the head and the upper neck load cell, the THOR-50M neck is connected to the head via three separate load paths: two cables (one anterior and one posterior) and a pin joint between the base of the head and the upper neck load cell. These load paths are independently instrumented, allowing the isolation of forces and moments on the components representing bone and ligament from the components representing muscles. This is expected to allow for improved injury prediction for the cervical spine because the abbreviated injury scale (AIS) 2+ injuries

to the cervical spine in motor vehicle crashes are most commonly fractures, so the ability to measure forces and moments acting on the bones and ligaments separately from the forces acting through the musculature allows a more accurate prediction of these fractures.

The Abbreviated Injury Scale (AIS) ranks individual injuries by body region on a scale of 1 to 6: 1=minor,

2=moderate, 3=serious, 4=severe, 5=critical, and 6=maximum (untreatable).

Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E., Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD. Docket ID NHTSA-2019-0106-0008,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0008.

The biomechanical basis of the THOR-50M neck design is well-established.

71 72

The construction of the THOR-50M neck allows the head to initially rotate relatively freely in the fore and aft directions. This allows the head/neck assembly to demonstrate the phenomenon known as head lag demonstrated by human volunteers in restrained frontal loading conditions, where the rotation of the head is delayed relative to the rotation of the neck.

This phenomenon results from the head initially translating forward with respect to the base of the neck, which is attached to the restrained torso. The change in angle of the head initially lags the change in angle of the line between the head and the neck but catches up by the time of peak excursion.

White RP., Zhoa Y., Rangarajan N., Haffner M., Eppinger R., Kleinberger M., “Development of an Instrumented Biofidelic Neck for the NHTSA Advanced Frontal Test Dummy,” The 15th International Technical Conference on the Enhanced Safety of Vehicles, Paper No. 96-210-W-19, 1996.

Hoofman, M., van Ratingen, M., and Wismans, J., “Evaluation of the Dynamic and Kinematic Performance of the THOR Dummy: Neck Performance,” Proceeding of the International Conference on the Biomechanics of Injury (IRCOBI) Conference, pp. 497-512, 1998.

Thunnissen, J., Wismans, J., Ewing, C.L., Thomas, D.J. (1995) Human Volunteer Head-Neck Response in Frontal Flexion: A New Analysis. 39th Stapp Car Crash Conference, SAE Paper # 952721.

The instrumentation in the neck assembly includes spring load cells which measure the compression at the anterior and posterior spring locations, six-axis load cells at the top and base of the neck to measure the forces and moments developed at these locations, and a rotary potentiometer at the occipital condyle pin to measure the relative rotation between the head and top of the neck. Due to the multiple load paths of the neck, comparing THOR-50M neck forces and moments to traditional single-load-path ATD designs is not straightforward; the THOR-50M instrumentation would require post-processing

to represent the total neck forces and moments in order to compare to the upper neck load cell measurements of a HIII-50M ATD. However, as described in the THOR-50M Injury Criteria Report,

post-processing of the neck for calculation of neck injury risk is not necessary.

GESAC, Inc (2005). Users Manual: THOR Instrumentation Data Processing Program, Version 2.3; Appendix C: Procedure for Calculating Head Loads at the Occipital Condyle from Neck Load Cell Measurements. National Highway Traffic Safety Administration.

Available at: https://one.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/THORTEST.zip.

Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E., Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD. Docket ID NHTSA-2019-0106-0008,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0008.

E. Chest

Throughout the development of the THOR-50M ATD, specific attention was given to the human-like response and injury prediction capability of the chest. Below we discuss the design and instrumentation of the THOR-50M chest.

1. Design

The THOR-50M's rib cage geometry is more realistic than the HIII-50M because the individual ribs are angled downward to better match the human rib orientation.

Biomechanical response requirements were selected to ensure human-like behavior in response to central chest impacts, oblique chest impacts, and steering rim impacts to the

rib cage and upper abdomen.

Better chest anthropometry means that the dummy's interaction with the restraint system is more representative of the interaction a human would experience.

Kent, R., Shaw, C.G., Lessley, D.J., Crandall, J.R. and Svensson, M.Y, “Comparison of Belted Hybrid III, THOR, and Cadaver Thoracic Responses in Oblique Frontal and Full Frontal Sled Tests,” Proc. SAE 2003 World Congress. Paper No. 2003-01-0160, 2003.

National Highway Traffic Safety Administration, “Biomechanical Response Requirements of the THOR NHTSA Advanced Frontal Dummy, Revision 2005.1,” Report No: GESAC-05-03, U.S. Department of Transportation, Washington, DC, March 2005. [

http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf.

The design of the THOR-50M includes a part known as a rib guide (472-3310) which is intended to prevent excessive downward motion of the anterior thorax during an impact. The rib guide is attached to the shoulder, and when there is downward motion of the ribs, the bottom of the rib damping material on rib #1 (the superior-most rib in the torso, 472-3310) can contact the top of the rib guide. Over time, this can result in an indent in the rib damping material. This indent has been observed on NHTSA-owned THOR-50M ATDs, but it has not been a concern as this is a sign of the rib guide performing its intended function. While this indent is not included on the drawing package, it is understood that an indent is acceptable as long as the qualification specifications (specifically, those of the upper thorax and lower thorax) are met, and it is not so deep that it allows metal-to-metal contact between the rib guide and the steel of the rib.

While Euro NCAP TB026 adopts the chest specified in the 2018 drawing package without any modifications, NHTSA is aware of two potential changes that have been discussed. Both of these changes appear to be intended to help ensure that the dummy is able to meet the upper thorax qualification response requirements. (The TB026 upper thorax qualification response requirements differ in a few ways from the proposed qualification requirements. This is discussed in more detail in Section V, Qualification Tests.)

The first change that has been discussed is a shorter rib guide. Humanetics Innovative Solutions, Inc. (Humanetics) reported to ISO WG5 (in June 2020) that while the indent on the damping material has been a known issue since the THOR-NT, it has led to concerns because it leads to issues meeting the Euro NCAP upper thorax qualification response requirements (specifically, the Z-axis upper rib deflection requirement) on a consistent basis. Humanetics has therefore suggested the use of a new, shorter rib guide which would allow more Z-axis deflection—primarily in the upper thorax qualification test, but presumably in other impact scenarios as well.

The second change is an additional rib performance specification. NHTSA is aware of a presentation made by the Japanese Automobile Manufacturers Association (in June 2020) to ISO WG5 describing an additional rib performance specification (

i.e.,

that would be specified in the drawing package) geared towards more consistently meeting the TB026 upper thorax qualification response requirements. The presentation included a procedure for an individual rib test using the same apparatus as the rib drop test for the ES-2re 50th percentile adult male side impact test dummy.

It noted data showing that the stiffness of the individual rib in the drop test was correlated with the thoracic impact response in the upper thorax qualification test condition.

49 CFR 572.185(b) Individual rib drop test.

NHTSA has tentatively decided not to implement either change. NHTSA's qualification testing of the dummy did not reveal any issues with meeting the proposed upper thorax qualification requirements, so we do not believe such changes are necessary. Moreover, before implementing the rib guide modification, it could be necessary to evaluate whether it would influence the dummy's response in biofidelity or thorax injury criteria test conditions. We do note, however, that the additional rib performance specification could be a useful way for ATD manufacturers to ensure that the fabricated ribs will result in an upper thorax qualification response consistent with upper thorax qualification specifications.

We seek comment on these issues. In particular, NHTSA requests comment from THOR-50M users who have evaluated alternative rib guide designs and have data to support equivalence of durability, repeatability and reproducibility, and equivalence of response in qualification, biofidelity, injury criteria, and vehicle crash test conditions.

2. Instrumentation

The THOR-50M is capable of measuring detailed information about how the chest responds in a crash. While the HIII-50M can measure chest deflection at only a single point (the sternum), the THOR-50M measures chest deflections at four points. This is useful because thoracic trauma imparted to restrained occupants does not always occur at the same location on the rib cage for all occupants in all frontal crashes.

Measuring deflection from multiple locations has been found to improve injury prediction,

and can improve the assessment of thoracic loading in a vehicle environment with advanced occupant restraint technologies.

While the HIII-50M measures the one-dimensional deflection at a single point, the THOR-50M can measure the three-dimensional position time-history for four points on the anterior rib cage relative to the local spine segment of rib origination, with two points on the upper chest, and two points on the lower chest. Between the upper and lower thorax instrumentation attachment points is a flexible joint (the Upper Thoracic Spine Flex Joint), so the reference coordinate system for the upper and lower thorax 3D motion measurements can change dynamically during a loading event. This instrumentation, coupled with its thoracic biofidelity,

provides the THOR-50M ATD with the ability to better predict thoracic injuries and to potentially drive more appropriate restraint system countermeasures.

Morgan, R.M., Eppinger, R.H., Haffner, M.P., Yoganandan, N., Pintar, F.A., Sances, A., Crandall, J.R., Pilkey, W.D., Klopp, G.S., Kallieris, D., Miltner, E., Mattern, R., Kuppa, S.M., and Sharpless, C.L., “Thoracic Trauma Assessment Formulations for Restrained Drivers in Simulated Frontal Impacts,” Proc. 38th Stapp Car Crash Conference, pp. 15-34. Society of Automotive Engineers, Warrendale, PA., 1994.

Kuppa, S., Eppinger, R., “Development of an Improved Thoracic Injury Criterion,” Proceedings of the 42nd Stapp Car Crash Conference, SAE No. 983153, 1998 (data set consisting of 71 human subjects in various restraint systems and crash severities).

Yoganandan, N., Pintar, F., Rinaldi, J., “Evaluation of the RibEye Deflection Measurement System in the 50th Percentile Hybrid III Dummy.” National Highway Traffic Safety Administration, DOT HS 811 102, March 2009.

Parent, D., Craig, M., Ridella, S., McFadden, J., “Thoracic Biofidelity Assessment of the THOR Mod Kit ATD,” The 23rd Enhanced Safety of Vehicles Conference, Paper No. 13-0327, 2013.

In addition to the deflection measurement system, the THOR-50M can also be instrumented with a uniaxial sternum accelerometer, triaxial accelerometers installed along the spine at the level of T1, T6, and T12, and a five-axis (three forces, two moments) load cell installed between the lumbar spine pitch change mechanism and the lumbar spine flex joint at the approximate anatomical level of T12. Clavicle loads cells can also be installed, but are not included in the THOR-50M described in the 2023 drawing package.

NHTSA is proposing to specify two deflection measurement devices, either of which NHTSA could choose, at its option, for use in the THOR-50M: the IR-TRACC and the S-Track.

IR-TRACC

The 2023 drawing package specifies a specific deflection measurement device, the Infrared Telescoping Rod for Assessment of Chest Compression (IR-

TRACC).

The IR-TRACC improved on the previous deflection measurement systems (CRUX—Compact Rotary Unit; DGSP—Double Gimbaled String Potentiometer) in many ways. The 2023 drawing package specifies six IR-TRACCs: four in the thorax and two in the abdomen.

Each IR-TRACC measures the absolute point-to-point distance along its length; this is used in the calculation of thorax and abdomen compression. The IR-TRACC is attached to two rotational potentiometers; this enables measurement of the three-dimensional position of the anterior attachment point at the rib or front of the abdomen relative to the attachment point at the spine.

Rouhana, S.W., Elhagediab, A.M., Chapp, J.J. “A high-speed sensor for measuring chest deflection in crash test dummies.” Proceedings: International Technical Conference on the Enhanced Safety of Vehicles. Vol. 1998, Paper No. 98-S9-O-15. National Highway Traffic Safety Administration, 1998.

See

SA572-S117 and SA572-S121.

While NHTSA has generally been satisfied with the performance of the IR-TRACC, the experience of NHTSA and other users with IR-TRACC-equipped THOR-50Ms has revealed a few potential issues. Vehicle manufacturers have raised several concerns about the performance and durability of the IR-TRACC, such as having to frequently repair or replace IR-TRACCs, and problems with the abdomen IR-TRACCs.

And during NHTSA-sponsored testing (particularly in the frontal oblique crash test mode), NHTSA observed abrupt decreases in the IR-TRACC voltage time-history.

We believe this is noise (and not a signal) because it occurs in all IR-TRACC voltage channels of a single ATD at the same points in time. As explained later in this document (Section VII.B.2) and in Appendix F to the preamble,

NHTSA testing has shown that once the IR-TRACC voltage signal is linearized, scaled, filtered, and converted to three-dimensional deflection, this noise is no longer evident. Nonetheless, this presents a risk of perceived or actual inaccuracies in thoracic and abdominal injury prediction during crash tests.

Alliance of Automobile Manufacturers, Inc. (2016). Technical Considerations Concerning NHTSA's Proposal to Rework the Agency's New Car Assessment Program (NCAP).

Regulations.gov

Docket ID NHTSA-2015-0119-0313, available at:

https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf.

See

Figure 1 in Hagedorn, A., Murach, M., Millis, W., McFadden, J., Parent, D., (2019). Comparison of the THOR-50M IR-TRACC Measurement Device to an Alternative S-Track Measurement Device. Proceedings of the Forty-Seventh International Workshop on Human Subjects for Biomechanical Research.

NHTSA is placing a separate document, “Supplemental Technical Appendices to Preamble,” in the docket for this rulemaking.

S-Track

In 2016 NHTSA issued a request for proposals for commercially-available devices capable of measuring the same or greater deflection range (roughly 90 millimeters of deflection for the thorax and 120 millimeters of deflection for the abdomen) within the same packaging space as the existing IR-TRACC devices.

Only one device—the S-Track—was identified. The S-Track, which is patented,

is produced by ATD-LabTech GmbH. (In 2022, Humanetics acquired ATD-LabTech.) Subsequent to the request for proposal, NHTSA also became aware of two additional deflection measurement devices: the KIR-TRACC, sold by Kistler Group, and the Spiral Track, sold by JASTI. NHTSA does not know whether these devices are congruent with the current THOR-50M parts and SA-drawings that describe the configuration and installation of IR-TRACCs. Because NHTSA became aware of these devices late in the development process (and neither was identified in NHTSA's request for proposals), they have not been considered for inclusion in the proposal, although NHTSA is considering evaluating whether they would be suitable instrumentation for the THOR-50M. Euro NCAP allows for installation of the IR-TRACC, the S-Track, and the KIR-TRACC.

National Highway Traffic Safety Administration (2016). IR-TRACC Direct Replacement Sensor. Solicitation Number DTNH2216Q00014, available at

https://sam.gov/opp/d505f6119f9a31bcdfa36607ed669e6b/view.

Pheifer, G. (2020).

U.S. Patent No. 10,713,974.

Washington, DC: U.S. Patent and Trademark Office.

European New Car Assessment Program (2022). Euro NCAP Supplier List, Appendices I & II, October 2022, TB 029,

available at: https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/.

The S-Track is similar to the IR-TRACC in that it is in-dummy instrumentation that attaches to the same points in the dummy as the IR-TRACC. Both measure linear displacement, and when coupled with the gimballed potentiometers, their signals can be post-processed to calculate three-dimensional motion. It differs in that the S-Track uses a mechanical scissor mechanism coupled to a linear potentiometer to measure linear motion along its axis, while the IR-TRACC uses a measurement of light transmittance, which requires a linearization calculation to estimate linear motion.

NHTSA has conducted a range of testing to evaluate the performance and equivalence of the S-Track. The testing, which included a partial qualification test series and sled tests, is briefly summarized below.

A more detailed discussion of this material is available in a previously published paper (except, as noted below, the second set of sled tests, for which a report is forthcoming).

This evaluation of alternate thorax and abdomen instrumentation only considered replacement of the displacement transducer component of the 3D IR-TRACC measurement system. Though it was not available at the time of purchase, a double gimbal kit to allow 3D measurement is now available from the S-Track manufacturer. ATD-Labtech GmbH (2017). 3D Adaption THOR-50th upper Thorax left 20_303. Available at:

https://www.atd-labtech.com/files/atd/uploads/produkte/s-track/produkte/4%20TH-3D-Adapter-Upper-Thorax-left/data_sheet-3D-Adaption_Thor-50th_upper_Thorax_left%20Rev%2001.PDF.

To evaluate whether the S-Track 3D adaption kit would result in equivalent measurement capabilities as the 3D IR-TRACC measurement system, the testing described here would be repeated, starting with the 3D static measurement assessment.

Hagedorn, A., Murach, M., Millis, W., McFadden, J., Parent, D., (2019). Comparison of the THOR-50M IR-TRACC Measurement Device to an Alternative S-Track Measurement Device. Proceedings of the Forty-Seventh International Workshop on Human Subjects for Biomechanical Research. Available at:

https://www-nrd.nhtsa.dot.gov/pdf/bio/proceedings/2019/Hagdeorn_S-Track_Biomechanics%20Workshop%202019_FINAL.pdf.

• The range and linearity of the S-Track and IR-TRACC sensors are comparable. The range of measurement of the S-Track is consistent with or larger than the range of measurement of the IR-TRACC, and all sensors were within the manufacturer's specification for the maximum allowable linear error as a percentage of full scale. This specification (0.5%) is tighter compared to the corresponding IR-TRACC specification (2%), though only one of the IR-TRACCs (right abdomen) showed a linearity error greater than 0.5%.

• Calibration and 3D static measurement assessments demonstrated similar or better accuracy compared to the IR-TRACC in the double-gimbal configuration for the upper left thorax, lower left thorax, and left abdomen. In the upper and lower thorax configurations, the S-Track showed less error than the IR-TRACC, and in the abdomen configuration, showed errors similar to the IR-TRACC.

• The form, fit, and function is comparable to the IR-TRACC. A full set of six S-Tracks was installed in a THOR-50M ATD. It did not present any connectivity or interference issues and appeared to be a plug-and-play replacement to the IR-TRACCs. One possible durability issue was identified

(damage to the cable at the base of the S-Track). This issue is mitigated if cable routing documentation is followed or the S-Track-specific double-gimbal assembly is used.

• The S-Track performed equivalently in qualification tests. NHTSA carried out the qualification tests for the body regions expected to be sensitive to a difference in thorax and abdomen instrumentation (upper thorax, lower thorax, and abdomen) on a THOR-50M in two different configurations: a baseline configuration with IR-TRACCs in all locations, and an alternate configuration with S-Tracks in all locations. Both configurations met the qualification targets for all of the test modes specified for those body regions, which demonstrates that the difference in measured deflections between the S-Track and IR-TRACC were well within expected test-to-test variation. In addition, the deflection time-history was qualitatively similar to the IR-TRACC.

• The S-Track performed equivalently to the IR-TRACC in most respects in a series of sled tests. NHTSA conducted sled tests in several conditions with the THOR-50M in two configurations: one with the IR-TRACC in all locations, and one with the S-Track in all locations:

○ The first series used a reinforced buck representative of the front half of a mid-sized passenger vehicle (including seat belt, frontal air bag, and side curtain air bag) and simulated a near-side frontal oblique (20 degrees) crash. The crash pulse was based on a frontal oblique crash test of the same vehicle. The S-Track proved to be durable and did not demonstrate the same noise artifacts as the IR-TRACC. The S-Tracks in the thorax showed similar measurements as the IR-TRACCs, particularly in the upper right thorax, the closest measurement location to the shoulder belt. There were some potential differences between the abdomen measurements, but abdominal deflection is not currently included as an injury criterion in FMVSS No. 208 and is not currently included in the rating calculation for frontal NCAP.

Additional evaluation would be desirable in cases where abdominal deflection is a critical measurement, such as a rear seat environment where submarining may be more likely to occur.

○ The second series of sled tests were conducted in the Gold Standard 1 (40 km/h, 12g peak pulse, standard lap and shoulder belt) and Gold Standard 2 (30km/h, 9g peak pulse, 3kN load limited shoulder belt) test conditions, which were used both in biofidelity assessment and in the development of thoracic injury criteria.

The goal of this testing was to determine if any differences occurred between the IR-TRACC and S-Track measurement devices, and if so, whether the magnitude of these differences would affect the biofidelity and injury criteria development analyses. NHTSA is preparing a report on this second series of sled tests, which will be placed in the research docket when it is complete.

The Gold Standard 1 test uses a flat rigid seat, standard lap and shoulder belts, knees restrained, and right front passenger restraint geometry. The Gold Standard 2 test uses a flat rigid seat, a force-limited shoulder belt and standard lap belt, knees restrained, and right front passenger restraint geometry.

Based on this testing and analysis, NHTSA believes that the S-Track is equivalent to the IR-TRACC (with the potential exception of the abdomen deflection in a sled test environment).

Proposal

NHTSA proposes to specify both the IR-TRACC and the S-track as permissible instrumentation for the THOR-50M. A THOR-50M configured with all IR-TRACCs or all S-tracks would conform to Part 572 and NHTSA could perform compliance testing with either device installed in the THOR-50M. The dummy has not been tested in a mixed configuration, with both devices installed (

e.g.,

IR-TRACCS in the chest and S-Tracks the abdomen, or with one IR-TRACC and three S-Tracks in the chest). The overall effects of such configurations are unknown. NHTSA seeks comment on whether the final specifications should allow such configurations. The IR-TRACC is specified in the 2023 drawing package (in SA572-S117 and SA572-S121). NHTSA has not yet published engineering drawings and parts packages to specify how the S-Track is installed in the dummy, but intends to integrate such documentation into the associated technical data package components upon finalization of this proposal. NHTSA seeks comment on this proposal.

F. Shoulder

The THOR-50M shoulder was developed to allow a human-like range of motion and includes a clavicle linkage intended to better represent the human shoulder interaction with shoulder belt restraints.

Clavicle load cells that can be installed in the proximal and distal ends of the clavicles are commercially available, but these load cells are not currently defined in the drawing package and NHTSA has not evaluated them.

Törnvall, F.V., Holmqvist, K., Davidsson, J., Svensson, M.Y., Håland, Y., Öhrn, H., “A New THOR Shoulder Design: A Comparison with Volunteers, the Hybrid III, and THOR NT,” Traffic Injury Prevention, 8:2, 205-215, 2007.

Below we discuss shoulder components for which NHTSA is proposing alternative permissible specifications (the alternate shoulder) or for which design modifications have been developed by external THOR-50M users but which NHTSA has tentatively decided not to incorporate in the drawing package (shoulder slip and coracoid process).

1. Alternate Shoulder Specification

Portions of the shoulder assembly specified in the 2018 drawing package (referred to as the SD-3 shoulder) are covered by a patent issued to Humanetics. However, for the reasons discussed in more detail in Section VIII, NHTSA has generally avoided specifying in Part 572 patented components or copyrighted designs without either securing agreement from the rights-holder for the free use of the item or to license it on reasonable terms or developing an alternative unencumbered by any rights claims. NHTSA has therefore designed, built, and tested an alternative design for a part of the shoulder assembly referred to as the shoulder pivot assembly that is not subject to any intellectual property claims. Accordingly, the proposed drawing package (the 2023 drawing package) includes specifications for the SD-3 shoulder pivot assembly as well as the alternate shoulder pivot assembly, so that either may be used. We explain this in more detail below.

SD-3 Shoulder

The SD-3 shoulder is notably different from the shoulder specified for the THOR-NT. The THOR-NT design includes a clavicle linkage attached by ball joints at the sternum and acromion, a linkage between the acromion and the scapula to which the upper arm attaches, and a linkage representing the scapula that attaches to the acromion linkage and the spine with unconstrained revolute joints. While there were some benefits of the THOR-NT design compared to existing ATDs at the time, the range of motion of the THOR-NT shoulder was found to be lacking compared to the human shoulder.

Shaw, G., Parent, D., Purtsezov, S., Lessley, D., Crandall, J., Tornvall, F., “Torso Deformation in Frontal Sled Tests: Comparison Between THOR-NT, THOR-NT with the Chalmers SD-1 Shoulder, and PMHS,” Proceedings of the International IRCOBI Conference, 2010.

An improved shoulder design was independently initiated by the Chalmers University of Technology (Chalmers), in

a project sponsored by Volvo and Autoliv, that sought to improve the prediction of occupant response in offset and oblique frontal crashes. Several prototype shoulder assemblies were constructed and evaluated, the most promising being labeled the Shoulder Design 1 (SD-1).

The SD-1 shoulder design includes a clavicle linkage with human-like geometry, connected by cardan joints to the sternum and acromion; a linkage representing the scapula that includes attachment to the upper arm; and a two-part linkage connecting the scapula to the spine which allows both upward and anterior motion of the shoulder assembly. The anterior rotation of the scapula linkage about a vertical shaft is governed by a coil spring within an assembly mounted to the spine box. Several rotation stops are installed throughout the assembly to prevent metal-to-metal contact at the extents of the range-of-motion.

Törnvall et al. (2007), 205-215.

After evaluation of the SD-1 in dynamic sled testing in comparison to the standard THOR-NT shoulder and to PMHS,

several improvements were proposed, including durability improvements to the humerus joint, decreasing the range of motion in the anterior and superior directions, and increasing the range of motion in the posterior and medial directions. The improved design, labelled as the SD-2 shoulder, was fabricated by GESAC to Chalmers' specifications, installed on a THOR-50M ATD, and evaluated in sled tests in the Gold Standard 1 and Gold Standard 2 conditions at the University of Virginia.

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Several additional durability and usability concerns were raised upon post-test inspection, including deformation of the joint between the clavicle and the acromion and hard contact to the humerus joint.

Shaw et al (2010).

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Crandall, J. (2013). ATD Thoracic Response: Effect of Shoulder Configuration on Thoracic Deflection. NHTSA Biomechanics Database, Report b11017R001,

available at: https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11017&index=1&database=B&type=R

Subsequently, an updated version of the SD-2 shoulder, known as the SD-3, was designed and fabricated as part of the European Union's Thoracic Injury Assessment for Improved Vehicle Safety (THORAX) project.

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Changes introduced in the SD-3 design included redesigned sterno-clavicular joint anthropometry, an updated shoulder cover, and improvements intended to address the durability and usability concerns raised by the University of Virginia testing. These latter improvements consisted of replacing the clavicle U-joint with a spherical joint; replacing the humerus joint with a metric version of the HIII-50M upper arm joint; and introducing a series of washers and bushings to the bottom of the vertical shaft to enable the resistance of the assembly to be adjusted to allow a more reproducible initial position.

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Lemmen, P., Been, B., Carroll, J., Hynd, D., Davidsson, J., Song, E., and Lecuyer, E. (2012). Development of an advanced frontal dummy thorax demonstrator. Proceedings of the 2012 IRCOBI Conference, Paper No. IRC-12-87, September 2012.

The SD-3 shoulder was installed on a THOR-50M ATD and sled testing was again carried out at the University of Virginia in the Gold Standard 1 and Gold Standard 2 conditions, as well as a variation of Gold Standard 1 with a force-limited belt.

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The SD-3 shoulder assembly was inspected in detail throughout this testing, and no evidence of damage was identified. The chest deflection and torso motion was similar to the SD-1 and SD-2 shoulders, while durability was improved. NHTSA also conducted an evaluation of blunt thoracic impact response of several configurations of THOR-50M ATDs and found the iteration with the SD-3 shoulder assembly installed to have the highest qualitative and quantitative biofidelity.

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Given these findings, NHTSA modified the drawing package to include the SD-3 shoulder. The first iteration of the drawing package to include the SD-3 shoulder was published as the September 2014 version.

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102

Crandall, J. (2013). ATD Thoracic Response: SD3 Shoulder Evaluation. NHTSA Biomechanics Database, Report b11470R001,

available at: https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11470&index=1&database=B&type=R

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Parent, D., Craig, M., Ridella, S., McFadden, J., “Thoracic Biofidelity Assessment of the THOR Mod Kit ATD,” The 23rd Enhanced Safety of Vehicles Conference, Paper No. 13-0327, 2013.

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National Highway Traffic Safety Administration (2014). THOR 50th Percentile Male Drawing Package, September 2014.

available at: https://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR%20Advanced%20Crash%20Test%20Dummy/thoradv/THOR-M_PDF_2014-09-29.pdf

After the publication of the September 2014 drawing package, Humanetics filed an application for a patent describing a shoulder assembly as well as an upper arm with an integrated load cell.

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Similar to the SD-3 shoulder, the design patent describes a shoulder pivot assembly which includes, among other things, a coil spring and an adjustable resistance element. After discussions between NHTSA and Humanetics, a disclaimer stating that portions of the THOR-50M drawings were covered by a Humanetics patent was added first to the NHTSA website where the drawings were available for download, and later to the drawings for the shoulder and upper arm assemblies in the drawing package itself.

105

Been, B., & Burleigh, M. (2017). U.S. Patent No. 9,799,234. Washington, DC: U.S. Patent and Trademark Office.

NHTSA has generally avoided specifying such parts, consistent with the legislative history of the Safety Act. (See Section VIII, Intellectual Property.) For this reason, as explained below we are also proposing, in addition to the SD-3 shoulder, an alternative shoulder pivot assembly design.

Alternate Shoulder Pivot Assembly Design

To address the potential issues with specifying only a proprietary shoulder design, NHTSA has designed, built, and tested an alternate shoulder pivot assembly that is not subject to any intellectual property claims. The alternate shoulder pivot assembly does not include any components to adjust the resistance of the assembly, and does not use a coil, clock, or watch-spring mechanism. Instead, the alternate shoulder pivot assembly design uses a molded rubber cylinder acting as a torsion bar. The top of the cylinder is attached to the shoulder support assembly and the bottom is attached to the spring housing, so rotation of the shoulder about the local Z-axis of the ATD results in torsion of the rubber cylinder. In order to adjust the resistance of the assembly, the springs must be removed and replaced.

NHTSA has evaluated the alternate shoulder in a variety of tests and tentatively concludes that its performance is similar to the SD-3 shoulder based on testing carried out to date. This testing, which included a partial qualification test series and sled tests, is briefly summarized below. A more detailed discussion of this material is available in a testing report that NHTSA is preparing, and which will be placed in the research docket when it is completed. NHTSA is also preparing another report that describes additional sled testing that was conducted; this report will be placed in the research docket when it is complete.

First, the alternate shoulder was installed in a THOR-50M without any issues regarding the form, fit, or function. Second, in a quasi-static rotation test, the alternate shoulder showed a similar moment-rotation loading slope to the SD-3 shoulder in both the forward and rearward rotation directions. Third, the SD-3 and alternate shoulder showed nearly identical longitudinal motion in all three loading directions in a quasi-static biofidelity evaluation comparing each

shoulder's range of motion to that of human volunteers; the responses of both were generally similar to the human volunteer response corridors. Fourth, the qualification tests most likely to be affected by shoulder response (upper thorax and chest) were carried out; the THOR-50M with the alternate shoulder met all qualification specifications for the upper thorax, and the force-deflection characteristic of the chest was nearly identical to that of a THOR-50M with the SD-3 shoulder. Finally, sled tests conducted in both a full frontal and a far-side oblique condition did not reveal any durability or usability issues, and the response of the THOR-50M with the alternate shoulder was within the test-to-test variation of the THOR-50M with the SD-3 shoulder.

NHTSA is therefore proposing the alternative shoulder as an acceptable optional subassembly. The shoulder assemblies are specified on drawings 472-3810 (left) and 472-3840 (right). Each shoulder assembly drawing specifies that either the SD-3 shoulder pivot assembly or the alternate shoulder pivot assembly may be used. The proposed specifications for the SD-3 shoulder pivot assembly are provided in drawings 472-3811 and 472-3841, and the proposed specifications for the alternate shoulder pivot assembly are provided in drawings 472-6810-1 and 472-6810-2. The drawing package currently indicates that the selection of which shoulder pivot assembly to use is made separately for the left and right shoulder assemblies, so that the dummy could be fitted with the SD-3 shoulder pivot assembly on one side, and the alternate shoulder pivot assembly on the other side. The dummy has not been tested in such a mixed configuration, and the overall effects of such configurations are unknown. NHTSA seeks comment on whether the final specifications should allow such mixed configurations.

NHTSA seeks comment on whether the final drawing package should include the SD3 shoulder, the alternate shoulder, or both. NHTSA also seeks comment from THOR-50M users who have evaluated the proposed alternate shoulder design, or other alternate shoulder designs, and have data related to equivalence with respect to durability, repeatability and reproducibility, and response in qualification, biofidelity, injury and vehicle crash test conditions.

2. Shoulder Slip

NHTSA is aware that some researchers and regulatory authorities have identified what they view as a possible design flaw in the shoulder—that the shoulder belt may slip towards the neck in a crash—and have developed potential modifications to the shoulder design to prevent this from happening.

This concern was first raised in a 2018 conference paper describing research conducted by Transport Canada. Transport Canada conducted a series of vehicle crash tests with the THOR-50M in the driver seat in two conditions: 40% offset and full frontal rigid barrier.

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It was reported that the upper portion of the shoulder belt could translate towards the neck and become entrapped in the gap between the neck and the shoulder. This occurred in 33 of the 45 offset tests and in 2 of the 13 full frontal rigid barrier tests. Compared to tests without shoulder belt slip, tests with shoulder belt slip showed higher measurements for lower neck shear (X-axis and Y-axis force), higher chest deflections in the upper left and lower right quadrants, and lower clavicle axial forces.

106

Tylko, S., Tang, K., Giguere, F., Bussieres, A. (2018). Effects of Shoulder-belt Slip on the Kinetics and Kinematics of THOR. Proceedings of the 2018 IRCOBI Conference.

Following that research, a 2019 Humanetics study identified and evaluated three prototype alternative modifications to the shoulder specified in the 2018 drawing package to prevent the shoulder belt from entering the gap between the neck and the shoulder.

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The study concluded that all three prototype modifications prevented belt entrapment and identified the preferred design alternative (referred to as a profiled split design). While the shoulder specified by NHTSA uses the same material for the entire shoulder pad, the profiled split design replaces the material closest to the neck with a higher-stiffness plastic material. This is intended to prevent the collar (the portion of the shoulder pad closest to the neck) from deforming and allowing the shoulder belt to slip towards the neck.

107

Wang, Z.J., Fu, S., McInnis, J., Arthur, J. (2019). Evaluation of Novel Designs to Address the Shoulder-belt Entrapment for THOR-50M ATD. Proceedings of the 2019 IRCOBI Conference.

In addition, in recent discussions with NHTSA, Euro NCAP has noted that several instances of shoulder belt slippage were observed in Euro NCAP testing as well as research tests with the mobile progressive deformable barrier. Euro NCAP reported that it was evaluating two potential shoulder design modifications, and expected these to be presented for approval in 2023.

While NHTSA has witnessed the shoulder belt moving towards the neck in vehicle crash tests, this phenomenon does not appear to influence dummy measurements related to injury criteria. NHTSA seeks comment on the desirability of and specifications for a modification to prevent belt slippage, including data on testing with the proposed shoulder design showing that it is leading to belt slippage that has a meaningful effect on test results. NHTSA also requests comment from THOR-50M users who have evaluated the split shoulder pad (or any available alternatives) and have data to support equivalence of durability, repeatability and reproducibility, and response in qualification, biofidelity, injury criteria, and vehicle crash test conditions.

G. Hands

The THOR-50M specified in the 2023 drawing package includes the same hand design as the HIII-50M. The drawing defining the hand assembly of the THOR-50M

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includes material formulation (Solid Vinyl, Formulation Portland Plastics, PM-7003) along with two two-dimensional images and one three-dimensional image of the hand. Additionally, the three-dimensional geometry of the hand assembly is included in the computer-aided design (CAD) files available through the NHTSA website in both Autodesk Inventor and generic STEP formats. However, the vinyl call-out does not sufficiently specify the hardness or the stiffness of the material formulation and may be insufficient to define the part. NHTSA therefore seeks comment on whether there is a need for a material test (

e.g.,

hardness measurement or a quasi-static compression test of a coupon of the material) or performance test (

e.g.,

quasi-static or dynamic impact to the as-fabricated hand) to further define the hand assembly of the THOR-50M, and if so, what the test might be.

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Drawing 472-6900-1/2.

H. Spine

The spine of the THOR-50M ATD is primarily constructed of steel. There are two flexible elements (one in the thoracic spine and one in the lumbar spine) that are intended to allow human-like spinal kinematics in both frontal and oblique loading conditions.

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Between the two flexible elements is a posture adjustment joint known as the lumbar spine pitch change mechanism, which allows the posture of the THOR-50M to be adjusted into various seating configurations in three-

degree increments, including, but not limited to, four designated positions (erect, neutral, slouched, and super slouched).

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The spine is instrumented with a five-axis thoracic spine load cell mounted below the lumbar spine pitch change mechanism and above the lumbar spine flex joint (a flexible joint that allows the dummy to go into flexion/extension in the lumbar region). Triaxial accelerometers can be installed in the nominal locations of the first, sixth, and twelfth thoracic vertebra.

109

Haffner, M., Rangarajan, N., Artis, M., Beach, D., Eppinger, R., Shams, T. (2001). Foundations and Elements of the NHTSA THOR Alpha ATD Design. The 17th International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 458.

110

See

Fig. 5-32 in the PADI.

The proposed spine design differs from the THOR-50M used by Euro NCAP. Whereas the 2023 drawing package specifies a lumbar spine pitch change mechanism, TB026 specifies a four-position lumbar spine box or an “alternative spine box” if “data has been provided to show equivalence between the NHTSA spine assembly and modified spine assembly.”

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Humanetics holds a patent on the four-position spine. The four-position lumbar spine is not specified further, but it does differ from the spine specified by the NHTSA drawings. The spine pitch change mechanism specified in the 2023 drawing package allows the spine to be set at a multitude of flexion or extension settings, not just four. NHTSA understands that the Euro NCAP design is intended to accommodate the in-dummy installation of some DAS brands by providing a mounting surface for data loggers. THOR-50M units built for Euro NCAP are configured with in-dummy DAS systems have the four-position spine.

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§ 1.4.3.

NHTSA has tentatively decided not to specify a lumbar spine pitch change mechanism limited to four positions for a few reasons. First, NHTSA has not inspected, nor has it performed any testing with, the four-position spine. Second, NHTSA generally avoids specifying patented components in Part 572 (see Section VIII, Intellectual Property). Third, the proposed spine specifications provide more adjustability than the four-position spine so the dummy may be used in a wider range of applications. NHTSA seeks comment on user experience with the four-position spine, including any data on equivalence with the THOR-50M as specified in the 2023 drawing package or biofidelity.

It is also NHTSA's understanding that members of Working Group 5 have observed variations in the ATD responses in the upper thorax qualification tests that have led to difficulties in meeting the Euro NCAP qualification specifications. Some manufacturers have suggested that this variation in response is due to variation in the spine flex joint (specifically, the vertical displacement (Z-axis) of the ribs is too high). One potential cause that has been identified (by Porsche in November 2019) is that that the hardness of the material comprising the spine flex joint was lower than the specification called for.

NHTSA's qualification testing did not reveal any issues with meeting the upper thorax qualification specifications (See Section V.D). In any case, in light of the potential concerns raised within Working Group 5 of possible excessive variation in the performance of the spine flex joint, potentially traceable to out-of-specification materials, NHTSA conducted a limited modeling exercise using the THOR-50M Finite Element (FE) model to investigate this. This analysis suggested that while variation in the lumbar and thoracic spine flex joints does influence the thoracic response in both qualification and sled test conditions, this variation is smaller than the expected test-to-test and ATD-to-ATD variation; specifically, a decrease in stiffness of the spine flex joints can influence the upper thorax qualification response, but by a much smaller magnitude than the width of the qualification specifications and test-to-test and ATD-to-ATD variations. For more information on this issue and NHTSA's FE modelling, please see Appendix B.

Nonetheless, a research effort is currently underway to assess the influence of the lumbar and thoracic spine flex joints in physical qualification tests (which would provide additional validation data to the computational analysis) and develop isolated dynamic tests of the lumbar and thoracic spine flex joints. Based on these results, NHTSA could potentially consider adding such a test(s) in the drawing package, qualification procedures, or laboratory test procedures. NHTSA requests comment from THOR-50M ATD users who have data to demonstrate variation in THOR-50M response that is believed to result from spine flex joint variation, specifically when the parts evaluated met the specifications of the THOR-50M drawing package. Additionally, NHTSA requests comment on the need for a thoracic spine and/or lumbar spine flex joint specification beyond the geometry and material properties defined in the drawing package.

I. Abdomen

The abdomen of the THOR-50M consists of two components, the upper abdomen and the lower abdomen. The lower abdomen is the region between the lower thoracic rib cage and the pelvis. The upper abdomen is the region on the dummy that represents the lower thoracic cavity, which fills the volume that exists between the lowest three ribs, above the lower abdomen and in front of the spine. The upper and lower abdomen components of THOR-50M are represented by structural fabric bags containing foam inserts which define the compression stiffness. Both abdomen inserts are anchored posteriorly to the spine, while the upper abdomen insert is additionally anchored to the lower rib cage. When the lumbar spine pitch change joint is set to the “slouched” position, the abdomen inserts are in contact with one another; when in the “erect” and “neutral” positions, the gap between the abdominal inserts is filled with the lower abdomen neutral/erect position foam. This gap is also spanned by two steel stiffeners on each side that are installed into the torso jacket. The bottom surface of the lower abdomen insert is coincident with the pelvis.

J. Pelvis

The THOR-50M pelvis is designed to represent human pelvis bone structure to better represent lap belt interaction,

112 113

and the pelvis flesh is designed to represent uncompressed geometry to allow human-like interaction of the pelvis flesh with the vehicle seat.

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The pelvis assembly is constructed of a steel and aluminum structure representing bone surrounded by a molded foam-filled vinyl covering representing flesh. The flesh is not physically connected to the pelvis bone but is held in place due to the tight fit of protrusions of the pelvis bone into recesses in the pelvis flesh, as well as circular bosses in the pelvis flesh into recesses in the pelvis bone. The pelvis flesh includes a portion of the upper thigh flesh, the interior surface of which includes gaps around the femur bone to allow articulation of the leg about the hip joint.

112

Reynolds, H., Snow, C., Young, J., “Spatial Geometry of the Human Pelvis,” U.S. Department of Transportation, Technical Report No. FAA-AM-82-9, 1982.

113

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The THOR-50M pelvis flesh is a molded component, with a vinyl outer

layer filled with expandable polyurethane foam. The two-dimensional drawing includes top, side, front, and isometric views of the molded pelvis flesh, while its three-dimensional geometry is included in the CAD files available through the NHTSA website in both Autodesk Inventor and generic STEP formats. The drawing package specifies part weight and foam density

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but not a material response or performance requirement for the pelvis flesh.

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Drawing 472-4100.

NHTSA is considering adding a performance specification for the pelvis flesh similar to that defined in the HIII-50M PADI. Such a performance specification would dictate the amount of allowable compression of the pelvis flesh under a defined load. A similar test was conducted on the pelvis flesh during the THOR Alpha design development.

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One such possible requirement would be the compression at a force of 500 N. Alternatively, Porsche has suggested a dynamic impact test using an impactor similar to that used in the upper thorax qualification test to impact the bottom of the pelvis flesh at a velocity of 2 m/s. NHTSA seeks comment on the need and specifications for a pelvis compression test, including whether it should be a qualification requirement, a drawing specification, or otherwise.

116

White Jr, R.P., Rangarajan, N., Haffner, M., “Development of the THOR Advanced Frontal Crash Test Dummy”, 34th Annual SAFE Symposium, Conference paper, 1996.

The pelvis is instrumented with bi-lateral triaxial load cells attached to the acetabulum (in order to measure the reaction force between the femur and the pelvis) and a triaxial accelerometer array at its center of gravity. The pelvis is also instrumented with bi-lateral anterior-superior iliac spine (ASIS) load cells that measure contact force in a nominally longitudinal axis and moment about a nominally lateral axis. The ASIS load cell is primarily used to measure the force transferred to the pelvis through the lap belt, in which case the moments can be used to determine the vertical level or center of pressure of the lap belt force.

K. Upper Leg

The upper leg assembly is constructed of steel and aluminum and includes a rubber compressive element at the middle of the femur shaft. This compressive element consists of a steel plunger that can translate axially along the femur shaft through a guide system. When the femur is loaded in axial compression (

e.g.,

pushing the knee towards the pelvis parallel to the femur), the motion of the plunger is resisted by a rubber element, which allows a human-like compression response.

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At the proximal end, the femur is connected to the pelvis through a ball joint in a socket attached to the acetabulum load cell. At the distal end, there is a six-axis load cell attaching the femur to the knee assembly.

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L. Knee

The THOR-50M knee is similar in construction to that of the HIII-50M, with a few differences. The primary structure of the knee cap is fabricated from aluminum, attached proximally to the femur load cell. Inside of the kneecap assembly, a slider mechanism is installed to allow translational motion of the tibia with respect to the knee. The knee slider includes a stop assembly to prevent metal-to-metal contact and to define the force-deflection characteristic of the tibia translation. Attached to the slider is a string potentiometer to measure the magnitude of tibia translation relative to the knee. The sides of the kneecap are enclosed by urethane covers to protect the slider mechanism, and the knee assembly is wrapped in a foam-filled vinyl cover representing knee flesh.

The design of the knee slider modifies the HIII-50M design by changing the geometry and material properties of the molded slider assemblies (472-5320 and 472-5330) and stop assemblies (472-5358).

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This change was made because at levels of knee displacement below the 10.2-millimeter (mm) biofidelity response requirement, the HIII-50M has been found to be stiffer than PMHS response corridors. Thus, during the THOR-50M Mod Kit project, biomechanical response requirements were specified with an additional measurement point at 5 mm of knee displacement with a force between 100 and 500 N. The Mod Kit also relegated the measurement point at 10.2 mm of deflection to a secondary requirement, as it was shown to be at the high end of the underlying PMHS corridors. While the 5 mm and 17.8 mm response requirements were met by the revised THOR-50M knee slider,

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the force-deflection response was below the human response corridor between 8 mm and 15 mm of deflection, but above the corridor after 18 mm of deflection.

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As such, when the biofidelity was evaluated using BioRank, the external biofidelity score of 2.282 indicated that the THOR-50M response was more than two standard deviations from the PMHS mean response. This BioRank score was lower than the corresponding HIII-50M score (1.070). This should be taken into consideration when using the THOR-50M to evaluate the risk of ligamentous knee injury.

118

Id.

at Figure 16.

119

Id.

120

See

Biofidelity Report, p. 254 (Fig. 45).

M. Lower Leg

The mechanical design of the THOR-50M lower extremity includes a compressive rubber section in the tibia shaft, similar to the compliant femur section, which provides more biofidelic force transmission from the heel to the knee. The spring damper Achilles tendon system aids in producing biofidelic ankle motion and torque characteristics. The ankle design allows rotation about three axes, representing inversion/eversion, dorsi/plantar-flexion, and axial rotation, and includes molded rubber elements to define the moment/rotation response and limit metal-to-metal contact at the extents of the range of motion. Different from existing ATDs, the THOR-50M includes a molded shoe design which integrates the foot and shoe into a single part. This feature, added in the 2016 update to the THOR-50M drawing package,

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is intended to reduce potential variability in the response of commercially available shoes.

121

National Highway Traffic Safety Administration (2016). Parts List and Drawings THOR-50M Advanced Frontal Crash Test Dummy THOR-50M Male August 2016. Docket ID NHTSA-2015-0119-0376.

Euro NCAP TB026 deviates from the proposed drawing package in that it specifies the HIII-50M lower legs, including the military specification

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shoes, knee slider sensor, and roller ball-bearing knees. We believe the THOR-50M specifications are preferable, for the reasons given above (

e.g.,

biofidelity).

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Specification is not stated in Euro NCAP TB026, but believed to be MIL-S-13192P as specified in 49 CFR 571.208 S8.1.8.2.

Each lower leg can be instrumented with five-channel load cells in the upper and lower tibia, a uniaxial load cell to measure the Achilles cable force, and three rotary potentiometers to measure the rotation of the individual ankle joints. Two uniaxial accelerometers can be mounted to the tibia and a tri-pack accelerometer assembly can be mounted to each foot plate.

N. Data Acquisition System

Testing with THOR-50M requires (as does testing with any dummy) a data

acquisition system (DAS). The data acquisition system performs signal conditioning, triggering, and data collection to store measurements from instrumentation installed in the dummy during a test into nonvolatile memory. As it relates to ATDs, there are effectively two types of DAS: external and internal (or in-dummy). As we explain below, while the 2018 drawing package does not specify a DAS (because it assumes the use of an external DAS), NHTSA is proposing to specify an optional in-dummy DAS.

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We note that the 2023 drawing package itself does not contain specifications for an in-dummy DAS. Instead, the proposed in-dummy DAS specifications are set out in an addendum that is being docketed along with the 2023 drawing package.

An external DAS is, as the name indicates, external to the dummy. The instrumentation in the dummy is connected to the external DAS via wires, sometimes referred to as an umbilical cable. The 2018 drawing package does not explicitly specify a DAS or related equipment, but the drawings assume an external DAS: they assume that the instrumentation wires are long enough to be bundled into an umbilical cable and connected to a DAS located in the lab or mounted to the vehicle in which the ATD is seated.

An internal DAS is installed within the dummy itself. An internal DAS has some advantages to an external DAS. The primary advantage is related to the mass properties of the dummy. With an internal DAS system, there are no external cables that may possibly affect body segment masses; segment masses are always the same no matter how the dummy is used. While upfront cost is higher, an internal DAS would reduce per-test costs, eliminate the need for interface cables to lab-specific DAS systems (which have been a frequent sources of instrumentation failures in research testing), and reduce the adjustments needed to arrive at the target test vehicle weight. Feedback from industry

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as well as Euro NCAP indicates that users prefer an in-dummy DAS for its many usability advantages. Euro NCAP TB026 requires an in-dummy DAS.

125

While Euro NCAP TB029 currently does not specify an approved in-dummy DAS,

126

earlier versions of TB029 did specify a few different approved in-dummy DAS systems.

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124

Alliance of Automobile Manufacturers, Inc. (2016). Technical Considerations Concerning NHTSA's Proposal to Rework the Agency's New Car Assessment Program (NCAP).

Regulations.gov

Docket ID NHTSA-2015-0119-0313, available at:

https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf.

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TB026 § 1.2.

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European New Car Assessment Programme (2022). Euro NCAP Supplier List, Version 4.0, October 2022, TB 029,

available at: https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/.

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European New Car Assessment Programme (2022). Euro NCAP Supplier List, Version 3.1, April 2021, TB 029,

available at: https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/.

The DTS TDAS G5, SLICE Nano, and SLICE6; the Kistler DTI, microDAU, and NXT32; and the Messring M=BUS.

In light of these potential advantages and user preferences, NHTSA sponsored development and testing of an in-dummy DAS. NHTSA published a request for solicitation for an in-dummy DAS.

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This was before Euro NCAP began testing with the THOR-50M. The solicitation favored a minimal redesign of existing THOR-50M parts, in order to facilitate interchangeability of parts between THOR-50Ms with and without in-dummy DASs. NHTSA contracted Diversified Technical Systems (DTS) to implement its SLICE6 data acquisition system in a NHTSA-owned THOR-50M. This included delivery of DAS components, replacement instrumentation compatible with the DAS, and replacement ATD parts to allow attachment of DAS components and preservation of inertial properties. The resulting implementation distributes a series of small 6‐channel data acquisition modules throughout the ATD, mounted directly on load cells or sensors where possible, or close to the sensor with short cables to the sensor. The DAS modules are chain‐networked with four wiring harnesses which connect to the SLICE6 Distributor, with a single ATD exit cable connecting the DAS to the full test system.

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National Highway Traffic Safety Administration (2017). Implement and Install THOR 50M In Dummy Data Acquisition System. Solicitation Number DTNH2217Q00033,

available at https://sam.gov/opp/068c7821de797ebe7f9e78a0f2b68dc4/view.

NHTSA evaluated the overall performance and equivalence of the THOR-50M with the in-dummy SLICE6 DAS in a full suite of qualification testing and a variety of sled and vehicle crash testing. This research and analysis is described briefly below. The vehicle crash testing is described in more detail in the cited report. NHTSA is preparing a report on the installation, qualification testing, and sled testing of the SLICE6 in-dummy DAS, which will be placed in the research docket when it is complete. Additional information on the durability of the THOR-50M with the in-dummy DAS system is included in Section VII.B, Durability and Maintenance.

• It was possible to install the SLICE6 into the dummy with negligible changes to the mass, moment of inertia, and center of gravity of the ATD and its individual body segments. This did require modifications to several THOR-50M parts (

e.g.,

the lower thoracic spine assembly) in order to allow attachment of the DAS hardware to the rigid components of the ATD.

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Saunders, J., Parent, D. (2023). Update on NHTSA's OMDB's half barrier analysis. Proceedings of the 27th Enhanced Safety of Vehicle Conference, Yokohama, Japan.

130

The OVSC Laboratory Test Procedures for FMVSS No. 208 specify an ambient temperature measured within 36 inches of the ATD to be between 69 and 72 degrees Fahrenheit. National Highway Traffic Safety Administration (2008). Laboratory Test Procedure for FMVSS 208, Occupant Crash Protection, TP208-14,

available at: https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/tp-208-14_tag.pdf.

• NHTSA has been able to fully qualify THOR-50M ATDs with the in-dummy DAS installed. Since the SLICE system has been installed, we have used the dummy in many tests and have qualified it with no issues. The THOR-50M with the in-dummy DAS was tested in simplified sled tests. Sled tests were conducted in the Gold Standard 1 (40 km/h, 12g peak pulse, standard lap and shoulder belt) and Gold Standard 2 (30km/h, 9g peak pulse, 3kN load limited shoulder belt) test conditions, which were used both in biofidelity assessment and in the development of thoracic injury criteria. The goal of this testing was to determine if any differences occurred between the external and internal DAS configurations, and if so, whether the magnitude of these differences would affect the biofidelity and injury criteria development analyses.

• NHTSA also tested the THOR-50M with an in-dummy DAS in a series of vehicle crash tests in the OMDB test condition with three different deformable barrier faces. While some of the OMDB tests appeared to show differences between the in-dummy DAS and umbilical configurations, it was not clear whether this was due to variation in the dummy response or variation in dummy positioning, vehicle response, and/or restraint system response.

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Importantly, this testing did not reveal any potential durability or usability issues associated with the in-dummy DAS, with one possible exception: The temperature inside the thoracic cavity of the ATD can increase beyond the ambient temperature typically prescribed for regulatory and consumer information crash tests.

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In a more recent set of vehicle crash tests, NHTSA closely monitored the rib temperature of the THOR-50M with the

in-dummy DAS.

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By routinely limiting the “ON” time of the DAS, NHTSA has been able to maintain the temperature range. Additionally, NHTSA has used a portable fume extractor device to aid in maintaining the temperature of the WorldSID-50M side impact dummy, which also has internal DAS system.

132 133

This device may also be employed in tests with the THOR-50M.

131

Saunders, J., Parent, D., Martin, P. (2023). THOR-50M fitness assessment in FMVSS No. 208 unbelted crash tests. Proceedings of the 27th Enhanced Safety of Vehicle Conference, Yokohama, Japan.

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Tatem, W., Louden, A. (2023). WorldSID-50M Fitness Assessment in FMVSS No. 214 Moving Deformable Barrier and Oblique Pole Crash Tests. Proceedings of the 27th Enhanced Safety of Vehicle Conference, Yokohama, Japan.

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This device is used to dissipate heat from the dummy in the pre-test setup (for example, while seating and positioning the dummy). Typically, a tube is inserted into the dummy jacket and in conjunction with the fan is used to vent heat from the dummy to maintain an in-spec internal temperature. The apparatus is detached from the dummy immediately prior to the vehicle or sled test. Use of such a fan may be specified in the OVSC laboratory test procedure.

Based on this testing, NHTSA has tentatively concluded that the THOR-50M with the in-dummy DAS is equivalent to one with the external DAS. NHTSA is therefore proposing an internal DAS as permitted optional instrumentation that it could use in its testing. This necessitates changes to the dummy to accommodate the DAS while ensuring that there are no changes to the mass, moment of inertia, and center of gravity of the ATD and its individual body segments. These changes may differ from the Euro NCAP approach specified in TB026, which permits the four-position spine box (discussed in Section III.H above) to accommodate the installation of some DAS brands by providing a mounting surface for data loggers. Euro NCAP does not provide part-by-part engineering drawings of the various DAS packages, which is necessary for THOR-50M to be sufficiently objective.

NHTSA has therefore provided, in an addendum to the 2023 drawing package, further specifications for the dummy to accommodate an internal DAS. It is anticipated that, upon finalization of this proposal, the in-dummy DAS drawings will be fully integrated within the relevant technical data package components. These specifications consist of descriptions of the instrumentation and new drawings for the dummy parts that require modifications to accommodate the DAS. The changes are specified such that the dummy with the in-dummy DAS will have the same inertial properties as the dummy using the external DAS. The drawings show DAS mass blanks in lieu of the actual DAS components (battery, data logger, etc.) with the exterior dimensions of the blank matching those of the corresponding SLICE6 component.

If an in-dummy DAS component is not installed (for example, if lower leg instrumentation is not needed for a given test mode), the blank would be filled with a material of a specified density. The material of the blank is not specified (although a reference specification is provided) but would be selected to provide an appropriate density and may also have internal flashing holes needed to attain the desired mass, which is chosen to match the mass of the actual DAS component. It is anticipated that, upon finalization of this proposal, the PADI will show two sets of installation steps: one with the “blank” component, and one with the actual DAS parts. (This two-set convention is also followed with load cells and their structural replacements). The proposed specifications are based on, but not necessarily limited to, the SLICE6 (the SLICE6 is not explicitly specified or called-out by name), so that another system fitting within the defined specifications could also be utilized.

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While we are aware of in-dummy DASs produced by other manufacturers, we have not evaluated whether these systems would be compatible with the in-dummy DAS addendum to the 2023 drawing package.

NHTSA seeks comment from users who have experience with both umbilical and in-dummy DAS configurations of the THOR-50M, as to whether they have seen any quantifiable differences between the two. NHTSA also seeks comment on whether any additional changes should be made to the proposed drawings specifying the in-dummy DAS to make it more amenable to additional DAS systems that are already in the field.

IV. Biofidelity

Biofidelity is a measure of how well the dummy replicates a human, and includes anthropometry, mass properties, range of motion, and impact response. The impact biofidelity is evaluated by comparing the response of the dummy to the response of a post-mortem human surrogate (PMHS or cadaver) or human volunteer in a variety of different test conditions (also referred to as test modes). Some of these tests focus on individual dummy components (head, neck, chest, abdomen, upper leg, knee, lower leg) and some evaluate the entire dummy as a complete assembly.

To evaluate the biofidelity of THOR-50M, NHTSA selected test conditions based on relevance to frontal and frontal oblique crash test applications and the availability of data. For example, a neck frontal flexion test was conducted by attaching the base of the THOR-50M neck to a sled and applying a certain acceleration pulse. This was then compared to the response measured on human volunteers who were subjected to a similar pulse. Specifically, the impact biofidelity of the THOR-50M was assessed in twenty-one test conditions. The test conditions are summarized in Table 6. Each test produces a series of data points (

e.g.,

force vs. time).

The test conditions have been developed over the years by various researchers to evaluate biofidelity and have been published in peer-reviewed journals. The PMHS and human volunteer response data generally comes from this published research. The THOR-50M response data comes from testing that NHTSA has been conducting on the THOR-50M throughout its development, all of which is available in NHTSA's Biomechanics Test Database.

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NHTSA also compared THOR-50M's biofidelity to that of the HIII-50M; many of the tests conducted with THOR-50M were paired with the same test conducted on the HIII-50M. In our testing we attempted to match the test conditions as closely as possible to the test conditions in the original PMHS or volunteer tests.

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Available at https://www.nhtsa.gov/research-data/research-testing-databases#/biomechanics.

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Overall, while some assumptions were necessary in the reproduction of the PMHS or volunteer test conditions, we believe that these assumptions should not affect the overall biofidelity assessment of the THOR-50M. For instance, NHTSA simplified some of the original tests in order to facilitate ease of testing when we expected the simplification to have a negligible influence on the result, such evaluating neck flexion using only the ATD's head and neck, and not the entire dummy. These assumptions and simplifications, as well as any limitations to our analyses, are discussed in detail in the docketed biofidelity report. Parent, D., Craig, M., Moorhouse, K. 2017. Biofidelity Evaluation of the THOR and Hybrid III 50th Percentile Male Frontal Impact Anthropomorphic Test Devices. Stapp Car Crash Journal, 61, 227-276,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0004.

Table 6—Biofidelity Conditions Considered in the Design of the HIII Frontal Dummies and THOR-50M ATDs

Body region

Test condition

Subpart E, O, W

THOR-50M

Head

Isolated Head Drop

•

Whole-body Head Impact

•

Face Rigid Bar

•

Face Rigid Disk

•

Neck

Neck Flexion, Pendulum

•

Neck Extension, Pendulum

•

Neck Frontal Flexion, Sled

•

Neck Lateral Flexion, Sled

•

Neck Torsion

•

Thorax

Sternal Impact, 6.7 m/s

•

Sternal Impact, 4.3 m/s

•

Lower Ribcage Oblique

•

Abdomen

Upper Abdomen Steering Rim

•

Lower Abdomen Rigid Bar

•

Abdomen Belt Loading

•

KTH

Femur Compression

•

Knee Shear

•

Lower Extremity

Dynamic Heel Impact

•

Tibia Axial Compression

•

Dynamic Dorsiflexion

•

Whole-body

Gold Standard 1

•

Gold Standard 2

•

Gold Standard 3

•

Far Side Oblique

•

The test conditions used to evaluate the THOR-50M represent an accumulation of biomechanics research. All conditions are accompanied by a well-specified, objective test procedure and a well-founded set of human response targets. The set of test conditions has grown substantially over the span of Part 572 rule makings. For example, in NHTSA's original 1998 proposal for the Subpart O HIII-5F dummy,

137

only six biofidelity conditions were assessed.

138

Since then, the list has grown substantially; new conditions have been developed for all body regions, and whole-body sled test conditions have been developed.

139

137

63 FR 46981.

138

Mertz, H.J., Irwin, A.L., Melvin, J.W., Stanaker, R.L., & Beebe, M. (1989). Size, weight and biomechanical impact response requirements for adult size small female and large male dummies (No. 890756). SAE Technical Paper.

139

See

available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf

) and Ridella, S., Parent, D., “Modifications to Improve the Durability, Usability, and Biofidelity of the THOR-NT Dummy,” The 22nd International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 11-0312, 2011.

NHTSA quantified how closely the response of the THOR-50M matched the response of the PMHS or human volunteers using the Biofidelity Ranking system (BioRank).

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BioRank has been applied in other instances cited in the literature

141

and in other NHTSA Part 572 rulemakings.

142

This methodology statistically compares the dummy response to the average PMHS/volunteer response (typically a time-series but sometimes a point estimate). A BioRank value of 0.0 indicates an ATD response identical to the average PMHS/volunteer response; a value of 1.0 indicates an ATD response that is on average one standard deviation

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away from the average PMHS/volunteer response; a value of 2.0 indicates an ATD that is on average two standard deviations away from the average PMHS/volunteer response; and so on. Therefore, the lower the BioRank value, the better the biofidelity. We computed BioRank scores for both the THOR-50M and the HIII-50M.

140

Rhule, H., Maltese, M., Donnelly, B., Eppinger, R., Brunner, J., Bolte, J. (2002) Development of a New Biofidelity Ranking System for Anthropomorphic Test Devices. Stapp Car Crash Journal 46: 477-512.

141

Rhule, H., Moorhouse, K., Donnelly, B., Stricklin, J. (2009) Comparison of WorldSID and ES-2RE Biofidelity Using Updated Biofidelity Ranking System. 21st ESV Conference, Paper No.09-0563.

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The analysis using Biorank described here mirrors (with some exceptions) the approach used in the assessment of the WorldSID 50th ATD.

See, e.g.,

80 FR 78522, 78538 (Dec. 16, 2015) (New Car Assessment Program Request for Comments); 71 FR 75304 (Dec. 14, 2006) (final rule for ES-2re Side Impact Crash Test Dummy 50th Percentile Adult Male); 71 FR 7534 (Dec. 14, 2006) (final rule for SID-IIs Side Impact Crash Test Dummy 5th Percentile Adult Female).

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The standard deviation is a statistic that measures the dispersion of a dataset relative to its mean.

For each body region, we calculated two BioRank scores: one for external biofidelity (the extent to which the ATD represents a human surrogate to the vehicle or restraint system); and one for internal biofidelity (the ability of the ATD to represent the human responses that relate to prediction of injury). External biofidelity measures are generally those recorded at the test fixture level, such as pendulum force or belt force; internal biofidelity measures are generally those recorded by the internal instrumentation of the ATD or test equipment such as motion tracking that records subject excursion.

NHTSA considered two other methods of quantifying biofidelity. One is the International Standards Organization (ISO) 9790 Biofidelity Classification System. ISO 9790 defines the analysis process, response corridors, and weighting factors for the quantitative assessment of biofidelity of side impact ATDs. Because the ISO 9790 response corridors and weighting factors are specific to side-impact ATDs, it could not be directly applied to a frontal impact ATD such as the THOR-50M, and we are not aware of a corollary ISO standard for assessment of frontal impact ATD biofidelity. While a method similar to that described in ISO 9790 could be developed to assess frontal impact ATD biofidelity, we believe such a method may introduce subjective bias because it contains many subjective features, including weighting

of test conditions and body regions.

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The BioRank system was developed to minimize subjectivity in the areas of corridor development, weighting, and scoring. Another method NHTSA considered is correlation and analysis (CORA), which may be a useful tool to carry out quantitative analysis.

145

However, the vast array of tunable parameters in the software can result in unintentional subjectivity and poor reproducibility. Further, there are no known and accepted relationships between CORA scores and biofidelity classifications. Accordingly, we evaluated biofidelity using BioRank.

144

Rhule, D., Rhule, H., Donnelly, B. (2005) The Process of Evaluation and Documentation of Crash Test Dummies for Part 572 of the Code of Federal Regulations. 19th ESV Conference, Paper No. 05-0284, pp. 9-10.

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Gehre C, Gades H, Wernicke P (2009) Objective rating of signals using test and simulation responses, The 21st International Technical Conference for the Enhanced Safety of Vehicles, Paper No. 09-0407, 2009.

We note that because many of the biofidelity test conditions utilize specialized instrumentation or test equipment, they are not intended to be carried out as certification or qualification tests conducted between crash tests or sets of crash tests to confirm that specified ATD response requirements are met. Instead, due to its relative complexity, biofidelity testing is carried out at the ATD design stage to assess the biofidelity of the design. Simplified and standardized versions of the biofidelity test conditions have been developed as qualification procedures for some body regions. Because the qualification response requirements are based on the expected variation in response of the ATD, not the underlying human response, the qualification requirements specify a much smaller allowable range in response than the biomechanical design targets. Therefore, it is expected that all THOR-50M units that meet the specifications of the qualification procedures would demonstrate similar biofidelity. The proposed qualification response requirements are discussed in Section V.

A full description of NHTSA's biofidelity testing and analysis can be found in the docketed biofidelity report.

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We note that there are no separate discussions in the report for the shoulder, spine, or pelvis. Impact biofidelity of the spine and pelvis, as well as the dynamic biofidelity of the shoulder, are intrinsically evaluated as part of the whole-body biofidelity sled test series.

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Shoulder biofidelity has also been assessed quasi-statically and found to be more similar to the human volunteer corridors than existing ATDs. NHTSA is finalizing a report on the alternate shoulder design, which includes the biofidelity evaluation described here; once complete, this report will be published to the research docket.

146

Parent, D., Craig, M., Moorhouse, K. 2017. Biofidelity Evaluation of the THOR and Hybrid III 50th Percentile Male Frontal Impact Anthropomorphic Test Devices. Stapp Car Crash Journal, 61, 227-276,

available at: https://www.regulations.gov/document/NHTSA-2019-0106-0004.

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The qualitative biofidelity of the shoulder is also discussed in the Biofidelity Report, where the role of the shoulder in belt retention (or lack thereof) is discussed qualitatively.

See

p. 272-273.

NHTSA believes that the THOR-50M is sufficiently biofidelic for incorporation into Part 572. The biofidelity report shows that the THOR-50M exhibits overall internal and external BioRank scores of below 2.0. See Table 7. Both internal and external BioRank scores are lower than those of the HIII-50M, which is defined in Part 572 (Subpart E) and used in regulatory and consumer information frontal impact crash testing. At the body region level, the internal and external BioRank scores for THOR-50M are all below 2.0 except for neck internal biofidelity and abdomen external biofidelity. The THOR-50M BioRank score for the neck and abdomen external biofidelity are, however, lower (better) than those for the HIII-50M. Overall, the internal BioRank scores for the THOR-50M were lower than those of HIII-50M in 5 of the 7 body regions evaluated, and THOR-50M external BioRank scores were lower than those of HIII-50M in 6 of the 7 body regions evaluated. Thus, the THOR-50M has generally improved biofidelity in the individual body region tests, which improves the accuracy of injury predictions. The THOR-50M and the HIII-50M have comparable quantitative biofidelity in the whole-body sled test conditions.

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This finding has been confirmed by independent research; a 2018 study showed that the HIII-50M and THOR-50M demonstrated similar biofidelity scores in a sled test environment representing a production vehicle.

See

Albert, Devon L., Stephanie M. Beeman, and Andrew R. Kemper. “Occupant kinematics of the Hybrid III, THOR-M, and postmortem human surrogates under various restraint conditions in full-scale frontal sled tests.” Traffic Injury Prevention 19.sup1 (2018): S50-S58.

Table 7—Body Region Internal and External BioRank Summary

Body region

THOR-50M

Internal

External

HIII-50M

Internal

External

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