Kazuo Higuchi, Senior Vice President
TK Holdings, Inc.
601 13th Street, NW
Suite 350 South
Washington, DC 20005
Dear Mr. Higuchi:
This letter is in response to your request for an interpretation of certain provisions of Federal Motor Vehicle Safety Standard (FMVSS) No. 209, Seat Belt Assemblies, as they relate to an inflatable seat belt you are developing. You request confirmation of your interpretation that during compliance testing, the inflatable portion of the device would be tested as a unit (not disassembled) when it is tested in accordance with S4.2(b). You also request confirmation of your interpretation that compliance with S4.1(d) would be evaluated in the pre-crash condition of your inflatable seat belt. Based on the information supplied to this agency and for the reasons explained below, we confirm both of your suggested interpretations.
By way of background, the National Highway Traffic Safety Administration (NHTSA) does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, now codified as 49 U.S.C. Chapter 301, it is the responsibility of the manufacturer to ensure that its vehicles and equipment comply with applicable requirements. Title 49 U.S.C. Chapter 301 authorizes NHTSA to develop and enforce FMVSSs applicable to new motor vehicles and new items of motor vehicle equipment, which require minimum levels of safety performance for motor vehicles. FMVSS No. 209 prescribes requirements for seat belt assemblies.
In your letter, you described an upper torso restraint that is intended to inflate in crashes above a specified severity. You stated that this inflatable seat belt assembly deploys in conjunction with a vehicles air bags and is intended for use in the front outboard seating positions of motor vehicles. Your letter stated that the inflatable portion of the upper torso restraint has a section of the assembly that crosses the upper torso consisting of an inflatable bladder enclosed in an internal fabric tube that is encased in an external fabric cover. In your letter you explained that, when deployed, one side of the external fabric cover tears open, allowing the internal bladder to inflate. Your letter further stated that upon inflation, the length of this section of the assembly is reduced with results similar to the pretensioning function of a conventional torso belt.
Paragraph S4.2 of FMVSS No. 209 specifies requirements for webbing. Under S4.2(b) webbing must withstand minimum force requirements without breaking, when tested pursuant to the procedures specified in S5.1(b). In your letter, you seek to confirm that during compliance testing, the inflatable portion of the seat belt would not be disassembled, i.e., that the inflatable portion of your inflatable seat belt assembly would be tested as a unit when it is tested in accordance with S4.2(b). We confirm that when conducting testing for compliance with FMVSS No. 209 S4.2(b), the agency would test the inflatable portion of the seat belt assembly as a single unit, and not disassemble it.
S4.1(d) specifies the following requirement: All hardware parts which contact under normal usage a person, clothing, or webbing shall be free from burrs and sharp edges. In your letter you stated that after the belt has inflated during a crash, and after the buckle is disengaged to permit egress from the vehicle, there may be a sharp edge that is isolated from the occupant, the occupants clothing and from any seat belt webbing. However, you also stated that prior to the inflatable portion of the belt inflating during a crash, there are no burrs or sharp edges on any parts of the hardware that can contact a vehicle occupant, clothing or the seat belt webbing. In your letter you stated your belief that it is this latter condition of the seat belt assembly that should be considered normal usage for purposes of compliance testing with S4.1(d). Normal usage is not defined in FMVSS No. 209, or any other FMVSS. Because the entire seat belt assembly must be replaced after deployment, and the inflatable seat belt is designed to deploy in conjunction with the air bag, NHTSA agrees that use of the uninflated, pre-deployment seat belt assembly is the normal usage of your inflatable seat belt assembly. Accordingly, when conducting testing for compliance with FMVSS No. 209 S4.1(d) the agency would test the seat belt assembly in its uninflated (pre-deployment) state.
We note that in preparing this interpretation, we have considered a number of issues related to FMVSS No. 209 and testing of inflatable seat belts, including issues specific to the inflatable seat belt design you described. It should not be considered as precedent for how we would address requests for interpretation with any differing facts.
If you have any further questions, please do not hesitate to contact Sarah Alves of my staff at (202) 366-2992.
Anthony M. Cooke