Interpretation ID: nht94-1.41

TYPE: Interpretation-NHTSA

DATE: February 7, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Cheryl Graham -- District Manager, Northeast Region, ARI

TITLE: None

ATTACHMT: Attached to letter dated 11/10/93 from Cheryl Graham to Chief Counsel's Office, NHTSA (OCC-9345)

TEXT:

We have received your letter of November 10, 1993, asking about the permissibility of aftermarket installation of an auxiliary pair of stop lamps "at each side of the rear window."

by way of background information the National Highway Traffic Safety Administration (NHTSA) issues Federal motor vehicle safety standards under the authority of the National Traffic and Motor Vehicle Safety Act (Safety Act). Under that Act, the sole res traint upon modifications to vehicles in use is that, if performed by a manufacturer, distributor, dealer, or motor vehicle repair business, the modifications must not "knowingly render inoperative, in whole or in part, any device or element of design in stalled on...a motor vehicle in compliance with an applicable Federal motor vehicle safety standard...." (15 U.S.C. 1397(a)(2)(A)).

In NHTSA's view, if the modifications tend to impair the safety effectiveness of the "device or element of design," then, at the minimum, a partial inoperability may have occurred within the meaning of the statutory prohibition. The question raised by y our letter, therefore, is whether the installation of the auxiliary stop lamps in that location would impair the effectiveness of the three original equipment stop lamps.

NHTSA decided to require the center highmounted stop lamp in addition to the then-existing original equipment two-lamp stop lamp system following research which indicated that a three-lamp system of this configuration was demonstrably more effective in p reventing rear end crashes than other rear end lighting systems that were tested, and considerably lower in cost. Included in the testing was a four-lamp system which incorporated two lamps at each side of the rear window, but no tests were conducted on the five-lamp system you describe.

The reasons for the better performance of the three-lamp system are unclear, but the triangular lighting array proved to be more effective than the trapezoidal four-lamp system (and more effective than a system tested which separated the usual stop lamp from the tail lamp).

Your customer appears to believe that the ability of following drivers to avoid rear end crashes is enhanced by a five-lamp stop lamp system. On the other hand, your proposed system, by incorporating the two lamps at each side of the rear window, would appear to change the lighting array.

We cannot say that the five-lamp system would either enhance or detract from safety. Thus, we cannot find that the additional lamps would "render inoperative" the original equipment three-lamp system, and it would be permissible under the regulations of this agency. However, the

permissibility of such a modification would be determinable under State law. We are unable to advise you on the laws of the various States and suggest that you write the American Association of Motor Vehicle Administrators for an interpretation. Its add ress is 4600 Wilson Boulevard, Arlington, VA 22203.

You have also asked "if the work is done improperly and results in an accident, where does the liability lie?" This question is a matter of state law, and we suggest that you consult a local attorney concerning it.