Interpretation ID: nht91-7.38

DATE: December 10, 1991

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA (Signature by Kenneth A. Weinstein)

TO: James E. Scapellato -- Director, Office of Motor Carrier Standards, FHWA

TITLE: Re Standard No. 108 (Heavy duty trailers) Lamps and Reflectors

TEXT:

This responds to your memorandum of November 20, 1991, asking whether Federal Motor Vehicle Safety Standard No. 108 permits a trailer manufacturer "to equip a heavy-duty flatbed trailer with amber tail lamps in combination with its rear turn signal lamps." Such a combination lamp would be adjacent to combination red stop and taillamps.

Standard No. 108 does not directly answer this question. Table II of the standard requires the trailer to be equipped with a pair of red taillamps. Section S5.1.3 of Standard No. 108 prohibits the installation of supplementary lighting equipment "that impairs the effectiveness of lighting equipment required by this standard." Thus, the question is whether the installation of amber taillamps would impair the effectiveness of the trailer's amber turn signal lamps, red stop lamps, and red taillamps. Although the determination of impairment is initially that of the vehicle's manufacturer in certifying compliance of the vehicle to all applicable Federal motor vehicle safety standards, NHTSA may review that determination, and, if clearly erroneous, inform the manufacturer of its views.

In this instance, NHTSA believes there is a substantial possibility of impairment of the effectiveness of other rear lamps. When combined with an amber turn signal lamp, the intensity of an amber taillamp might mask the turn signal in operation. Because motorists are not used to seeing steady burning amber lamps on the rear of vehicles, amber taillamps could lead to momentary confusion of a driver following the trailer when the stop lamps are activated, thereby impairing the effectiveness of the stop signal. The presence of simultaneously burning amber and red taillamps could also create some confusion of a following driver approaching the trailer from around a corner to its rear. Thus, we have concluded that a combination amber turn signal and taillamp is implicitly prohibited by Standard No. 108.