The NHTSA Issue a Proposal to Amend Anthropomorphic Test Devices
The National Highway Traffic Administration (NHTSA) published a Notice of Proposed Rulemaking (NPRM) in the September 7, 2023 Federal Register (F.R. Vol. 88 No. 172; 49 CFR PART 572 Docket No. NHTSA-2023-0031). This NPRM would 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). This 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 for use in frontal crash compliance tests.
The NHTSA and the broader vehicle safety community uses crash test dummies in a variety of ways. NHTSA uses crash test dummies to test vehicles for compliance with Federal Motor Vehicle Safety Standards (FMVSSs), to determine vehicle crashworthiness ratings for the New Car Assessment Program's (NCAP) 5-Star Safety Ratings, and to conduct vehicle safety research. Regulatory authorities in other countries and regions, third-party vehicle rating programs, motor vehicle and equipment manufacturers, and others use crash dummies to evaluate vehicle safety and design safer vehicles and equipment.
Now, the NHTSA uses the devices specified in 49 CFR Part 572, Anthropomorphic Test Devices to test for FMVSS compliance and NCAP performance. Part 572 provides detailed design information, engineering drawings and procedures for assembly and inspection. NHTSA has codified numerous dummies that range in sex, size, age, and measurement capability. The 50th percentile male dummy currently defined in Part 572 for frontal impacts is the Hybrid III-50M. NHTSA added the HIII-50M to Part 572 in 1986. 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, it is anticipated that a rulemaking proposal will be published in the near future to add the THOR-05F to Part 572.
Improvements for the THOR-50M include more human-like occupant response in a crash and advanced instrumentation. These attributes enable it to better predict the risk of injury to human occupants which should help vehicle designers develop and test improved occupant restraint systems as well as types of novel vehicle seating configurations likely to be used in highly automated vehicles. The NHTSA has tentatively concluded that the THOR-50M is sufficiently biofidelic, exhibits repeatable and reproducible performance, and is sufficiently durable. The European New Car Assessment Program (Euro NCAP) has officially adopted the THOR-50M and is currently rating vehicles using this dummy. The Economic Commission for Europe is considering adopting the THOR-50M for use in frontal crash testing under its vehicle safety regulations. The NHTSA believes that the THOR-50M's enhancements will lead to more effective restraint system designs and allow more informative comparisons of the safety of different vehicles. Additionally, the fact that manufacturers are already using this dummy, leads the NHTSA to believe vehicle manufacturers will choose to certify vehicles to FMVSS No. 208 using the THOR-50M. The 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.
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 - 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.
- 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.
- Improved evaluation of vehicle performance -The above enhancements allow the THOR-50M to better differentiate the performance of different vehicles and restraint systems. The more sophisticated measurement capabilities of the advanced system are better suited to develop and test more sophisticated and highly tunable contemporary restraint systems. Motor vehicle manufacturers and restraint suppliers have already used the THOR-50M to evaluate vehicle crashworthiness and develop occupant protection countermeasures.
Other possible benefits of using the THOR-50M include that it is well-suited for possible 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 used in a range of applications beyond FMVSS compliance testing (e.g., 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. Examples include consumer information crash testing, standards and regulations in other transportation modes, and research; therefore, 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.
The 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. The NHTSA seeks comment on whether the THOR-50M is sufficiently specified to ensure that dummies are uniform and will provide repeatable and reproducible measurements. The NHTSA also seeks comment on whether it would be useful to end-users of the dummy if NHTSA created a list of suppliers used by the 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). This information would not be incorporated into Part 572, but would be provided as a reference for users and could be periodically updated by the NHTSA.
Testing with THOR-50M requires a Data Acquisition System (DAS). The DAS 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). The 2018 drawing package does not specify a DAS because it assumed the use of an external DAS. Based on their testing, the NHTSA has tentatively concluded that the THOR-50M with the in-dummy DAS is equivalent to one with the external DAS, and is therefore proposing an internal DAS as permitted optional instrumentation. 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 systems. The NHTSA also seeks comment on if 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.
NHTSA's investigation of the sources of variability provided additional confidence that the proposed acceptance intervals are both achievable and sufficient to ensure that the dummy is providing uniform responses. The NHTSA seeks comment on this methodology. Although the qualification docketed report "THOR-50M Repeatability and Reproducibility of Qualification Tests'' (R&R Report) utilizes only NHTSA's test data, the NHTSA is open to considering qualification data provided by commenters in the finalization of the qualification specifications, provided that the data are from THOR-50M ATDs conforming to the 2023 drawing package and the data was collected following the proposed Qualification Procedure.
Other items that the NHTSA request comments on include:
- 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.
- The NHTSA might consider changing the qualification targets to reflect the larger population of THOR-50M units in the field, depending on any change that it could have on the biofidelity of the dummy and the applicability of injury risk functions.
- Qualification testing - should the qualification procedures be incorporated by reference, or whether it would be preferable to locate a much-simplified set of qualification procedures directly in Part 572 and put additional detail and documentation in the Office of Vehicle Safety Compliance (OVSC) laboratory test manual or similar document that would not be incorporated by reference but instead provided as guidance to DOT contractors and other ATD end users?
Comments for this proposal need to be submitted not later than November 6, 2023. The NHTSA are proposing that the Final Rule would be effective on publication in the Federal Register.
The NHTSA NPRM is available on InterRegs.NET for our US Federal subscribers and is also available at www.selectregs.com.