Interpretation ID: nht78-2.18

DATE: 12/04/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Department of the Army

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of November 13, 1978, to the Administrator questioning whether certain trucks procured by your Command comply with paragraph S4.5.4 of Federal Motor Vehicle Safety Standard No. 108.

That paragraph states "The stop lamps on each vehicle shall be activated upon application of the service brakes." You wrote that "when the hazard warning lights are activated the stop lamp cannot be activated upon application of the service brakes." The system you describe would be in compliance with Standard No. 108, if the stop lamps and signal lamps are optically combined, for the following reasons. Paragraph S4.4.1 allows combination of a stop lamp with a turn signal lamp (which provides the hazard warning signal). Paragraph 4.2 of SAE Standard J586c Stop Lamps, August 1970 (incorporated by reference in Standard No. 108 as the operative standard for stop lamps) requires that "When a stop signal is optically combined with the turn signal, the circuit shall be such that the stop signal cannot be turned on in the turn signal which is flashing."

This, of course, means that in a combination lamp the stop signal cannot be given while the hazard warning signal is being operated. If the Army deems it desirable it could require a different circuitry in combination lamps by which the stop lamps and hazard warning signal lamps could operate simultaneously, as military vehicles need not conform to Federal safety standards (49 CFR 571.7(c)).

Because several jurisdictions require slow-moving vehicles to use the hazard lamps while in motion, I am asking our Office of Rulemaking to review this prohibition. Thank you for bringing this matter to our attention.

SINCERELY,

DEPARTMENT OF THE ARMY

US ARMY TANK-AUTOMOTIVE MATERIEL READINESS COMMAND

NOVEMBER 13, 1978

Administrator National Highway Traffic Safety Admin

Dear Ms. Claybrook

Reference is made to FMVSS 108, paragraph S4.5.4.

Reference paragraph states "The stop lamps on each vehicle shall be activated upon application of the service brakes."

Inspection of the lighting system in some commercial trucks recently procured by this Command disclosed that when the hazard warning lights are activated the stop lamp cannot be activated upon application of the service brakes.

While it is recognized that the primary purpose of hazard warning lights is to warn approaching traffic of a disabled vehicle, several states require the use of hazard warning signal for slow moving vehicles, i.e, NY Thruway, and Pennsylvania Turnpike. Application of the service brakes under this condition would not activate the stop lamps to warn following traffic.

Request this office be provided the DOT position as to whether or not the system described above meets the requirements of FMVSS 108, S4.5.4.

ROBERT J. SHIROCK Safety Director