Mr. Yoshiaki Matsui
Manager, Automotive Equipment
Legal & Homologation Section
Stanley Electric Co. Ltd.
2-9-13, Nakameguro, Meguro-ku
Tokyo 153, Japan

Dear Mr. Matsui:

We have received your letter of March 13, 1996, asking for an interpretation of the word "replaceable" with respect to the replaceable light sources permitted by Motor Vehicle Safety Standard No. 108 for use in motor vehicle headlamps. This information will assist you in the development of HID headlamps.

You ask whether "replaceable" as used in paragraph S7.7 means that access should be provided for convenient replacement without the use of special tools, which is a specific requirement of Standard No. 108 for light sources for the center highmounted stop lamp. The answer is no; there is no requirement that replaceable light sources be replaceable without the use of special tools.

We recognize that HID light sources may be designed for the life of the vehicle on which they are installed, and, optimally, would require replacement only in the event of front end damage. However, NHTSA believes it is in the interest of safety that light sources that are not designed for such longevity should be replaceable in a simple manner. When the agency amended Standard No. 108 to permit replaceable light sources (48 FR 24690, June 2, 1983), the replaceable light sources that were initially produced had bayonet mountings, which provided positive one-way insertion of the bulb into the reflector assembly. This allowed owner-replacement of the light source, a safety benefit used in justification of the final rule: "The easy replacement of the bulb may result in faster replacement of burned out headlamps." Thirteen years later, headlighting systems have become more complicated in a way that the agency did not foresee then, but the principle of simplicity of replacement of the light source remains.

If you have further questions you may refer them to Taylor Vinson of this Office (FAX 202-366-3820).


Samuel J. Dubbin Chief Counsel ref:108 d:4/24/96