Interpretation ID: nht89-1.30

TYPE: INTERPRETATION-NHTSA

DATE: 03/02/89

FROM: ERIKA Z. JONES -- CHIEF COUNSEL NHTSA

TO: ROBERT J. LATUS -- POSTMASTER U.S. POST OFFICE

TITLE: NONE

ATTACHMT: LETTER DATED 12/07/88 FROM ROBERT J. LATUS TO NHTSA, SUBJECT PRIMARY BRAKE LIGHT, OCC 2942

TEXT: Dear Mr. Latus:

This is in reply to your letter of December 7, 1988, regarding the functioning of stop lamps on a 1989 Oldsmobile Ciera car. You reported that the hazard warning lamps override the stop lamps on this model when both lamps are activated simultaneously. You have been informed that this is a new federal regulation. You have asked us to explain the regulation, reporting that foreign cars do not seem to present the problem you have identified.

At the outset, it may be helpful if we explain the applicable regulation, which is Federal Motor Vehicle Safety Standard 108. Under this standard, hazard warning systems are installed for use to indicate a disabled or slow moving vehicle in the roadway ahead. They ordinarily operate through the turn signal lamps, which can be either amber or red in color. In those rear lighting configurations where the turn signal lamps are red, they are frequently combined with stop lamps. (Combined lamps are those that share a common compartment and lens.) Under our standard, in a combined system the turn signals are required to take precedence over the stop lamps when both are activated. However, the rule does not specify a required order of precedence between the hazard warning lamps and the stop lamps. The stop lamps may be overridden by the hazard warning lamps when both are activated simultaneously, or the stop lamps may continue to operate and override the hazard warning signals. Our standard has allowe d either method of operation since it was first promulgated in 1968. Thus, there has been no change in the applicable regulation. As to your comment about foreign cars, it is our understanding that a large percentage of imported vehicles use amber rear turn signal and hazard warning systems, in which case the stop lamps and turn signal lamps are not combined. Therefore, both would operate independently when both are activated.

Since our standard allows both methods of operation, your dealer may legally modify the vehicle so that the primary stop lamps take priority if they and the hazard lamps are activated simultaneously. However, the

dealer may not legally alter the car is such a way that the alteration permits the primary stop lamps to override the turn signals if both are activated simultaneously.

We appreciate your interest in safety, and I hope that this answers your questions.

Sincerely,