Mr. Kevin Ro

National Manager, Technical &

  Regulatory Affairs, Safety

Toyota Motor North America, Inc.

601 Thirteenth Street, NW, Suite 910 South

Washington, DC  20005


Dear Mr. Ro:


This letter responds to Toyota’s request for an interpretation of the requirements associated with advanced air bags equipped with multistage inflators.  You state Toyota’s belief that the term “multistage inflator,” as used in Federal Motor Vehicle Safety Standard (FMVSS) No. 208, Occupant Crash Protection, is not intended to be design-restrictive, but intended to characterize various designs of advanced air bags with decision-based deployment strategies that result in different levels of air bag internal pressure.  You request NHTSA’s confirmation that technologies that are other than or in addition to the types of technologies traditionally used as multistage inflators that function to adjust air bag pressure based on occupant classification can be used to meet the low risk deployment requirements of FMVSS No. 208.  You have provided an example of one such technology to NHTSA under a claim of confidentiality.  As explained below, NHTSA agrees with you that the term “multistage inflator” should be interpreted broadly to encompass any type of technology that adjusts air bag pressure based on occupant classification.


By way of background, on May 12, 2000, NHTSA published a final rule in the Federal Register (65 FR 30680) requiring advanced air bags in all passenger cars, multi-purpose vehicles, light trucks, and buses with a gross vehicle weight rating of 3,855 kilograms (8,500 pounds) or less and an unloaded vehicle weight of 2,495 kilograms (5,500 pounds) or less.  That final rule established advanced air bag performance requirements to minimize the risk of injury to children, as well as new requirements to enhance protection of small and mid-sized adults.  Pertinent to your question, S21 and S23 provide three options for compliance – low risk deployment, automatic suppression, or dynamic automatic suppression.  Your question concerns the low risk deployment option with respect to the testing of 3-year-old and 6-year-old child test dummies.


In the test procedure for the low risk deployment option for the 3-year-old and 6-year-old test dummies (S22.4.4 and S24.4.4), the regulation states that “[i]f the frontal air bag system contains a multistage inflator, the vehicle shall be able to comply with the injury criteria at any stage or combination of stages or time delay between successive stages that could occur in a

rigid barrier crash test at or below 26 km/h (16 mph), under the test procedure specified in S22.5.”  The test procedure specified in S22.5 (the indicant test) is used in determining the stages that are fired for use in the low risk deployment test.


In the May 2000 final rule (65 FR 30688), the agency expressed an intent to avoid adopting requirements that might be overly design restrictive that would make it difficult for vehicle manufacturers to design their air bags to perform well in both rigid barrier tests and the wide range of real world crashes.  In keeping with that sentiment, we interpret the term “multistage inflator” broadly to encompass any type of technology that adjusts air bag pressure as a function of time based on factors such as occupant classification and vehicle crash pulse.  The successive variations in deployment levels, regardless of the type of technology that causes them, are considered to be the “stages” of deployment.  Thus, the low risk deployment test would apply to these new technologies that may be used in lieu of or in combination with traditional multistage inflators.  In NHTSA’s compliance testing, we have already observed examples of advanced deployment technologies, and have determined that these technologies can satisfy the low risk deployment requirements, provided, of course, the systems meet the specified performance requirements.


I hope this information is helpful.  If you have any further questions about this issue, please feel free to contact David Jasinski of my office at (202) 366-2992.


                                                                                    Sincerely yours,




                                                                                    O. Kevin Vincent

                                                                                    Chief Counsel


Dated: 9/20/13

Ref: Standard No. 208