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Interpretation ID: Toyota_knee_bolster

    Chris Tinto, Director, Technical & Regulatory Affairs
    Toyota Motor North America, Inc.
    1850 M Street, NW Suite 600
    Washington, DC 20036


    Dear Mr. Tinto:

    This responds to your request for an interpretation regarding the definition of "air bag system" as it pertains to test procedures specified in our occupant crash protection standard. Your letter asked if an inflatable knee bolster would be considered part of the "driver frontal air bag system" under the procedure for low risk deployment (LRD) tests of the driver air bag. As explained below, for purposes of LRD tests, the driver frontal air bag system refers to the steering wheel hub-mounted inflatable restraint and does not include an inflatable knee bolster.

    On May 12, 2000, the National Highway Traffic Safety Administration (NHTSA) amended Federal Motor Vehicle Safety Standard (FMVSS) No. 208 to minimize the risk of injury from deploying air bags for small adults and children (65 Federal Register 30680; Advanced air bag rule). The Advanced Air Bag Rule adopted a LRD test to address the risk air bags pose to out-of-position occupants, particularly those of small stature. The test is performed by activating a frontal air bag system with a test dummy in "worst case" positions: placing the dummys chin on the module and for the 5th percentile adult female test dummy, also placing the dummy's chin on the steering wheel.

    In your letter you stated that Toyota has equipped some of its vehicles with a knee air bag (knee bolster), which deploys in a frontal crash along with the driver air bag located in the steering wheel hub. You further stated that Toyota considers a knee bolster part of the frontal air bag system and therefore, it should be deployed during a LRD test. Your letter also noted that both the knee bolster and the air bag located in the steering wheel hub deploy in the rigid barrier test described in S22.5 of FMVSS No. 208, which determines the deployment stage for the LRD procedure in S26.

    In a November 19, 2003, final rule, the agency specifically addressed which air bag system components are fired in a LRD test. The agency stated that:

    While neither "air bag [system]" or "inflatable restraint [system]" is defined in FMVSS No. 208 or any other place in 49 CFR Part 571, the intent of the term "air bag" is to describe the components that make up the passenger- side dash-mounted and driver-side steering wheel hub-mounted, inflatable restraints used for occupant protection in a frontal impact. This does not refer to any other pyrotechnic system such as a belt pretensioner or inflatable knee bolster (68 Federal Register 65179, 65186; emphasis added).

    We further stated that the agency has no data on the effect deploying devices other than the frontal air bag will have on the LRD test procedure. We also do not have any data on the performance of any of these other pyrotechnic devices for out-of-position occupants in the field. Specifically, we are concerned that inflatable knee bolsters could negatively impact the repeatability of the LRD tests, even though they would inflate in a real crash. Therefore, when the agency performs a LRD test on a vehicle equipped with inflatable knee bolsters, the knee bolsters are not inflated.

    If you have any further questions, please contact Mr. Chris Calamita of my staff at (202) 366-2992.

    Sincerely,

    Jacqueline Glassman
    Chief Counsel

    ref:208
    d.7/19/04