Interpretation ID: 17684.ztv

Mr. Peter Gross
Electrical Engineer
Spartan Motors
P.O. Box 440
Charlotte, MI 48813

Dear Mr. Gross:

We are replying to your letter of March 25, 1998, asking a question regarding motor vehicle lighting on motor homes wider than 80 inches, which will have rear combination stop/turn signal lamps. Specifically, you write that "when the hazard warning lights are activated the brake signal will not override the flashing tail lamps" (we believe you mean flashing turn signal lamps). You state that this is inconsistent with all vehicles Spartan has built with rear combination stop/turn signal lamps and inquire whether the lack of override is acceptable.

The stop lamp and turn signal lamp standards that apply to vehicles whose overall width is 80 inches or more are incorporated by reference in Standard No. 108, and are, respectively, SAE Standard J1398 MAY85 Stop Lamps For Use on Motor Vehicles 2032 mm Or More In Overall Width, and SAE Standard J1395 APR85 Turn Signal Lamps For Use on Motor Vehicles 2032 mm Or More In Overall Width. Paragraph 5.4.2 of both J1398 and J1395 address the performance priorities of combination stop/turn signal lamps. These paragraphs state 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 if the turn signal is flashing" (the same is required by paragraphs 5.4.2 of SAE J586 FEB84 and SAE J588 NOV84 for combination stop/turn signal lamps on narrower vehicles). Because hazard warning signal lamps operate through the turn signal lamp system, many vehicles are wired so that the stop signal cannot be turned on if all the turn signal lamps (i.e., the hazard warning lamp system) are flashing.

However, Standard No. 108 and the SAE have no requirements per se for the hazard warning system. This means that a vehicle may be wired with a separate hazard warning system circuit so that it is subordinate to, and overriden by, the stop signal when both are operated simultaneously.

However, the stop lamp must not override the individual turn signals when they are operating simultaneously. This may explain the apparent inconsistency that you noted in Spartan production.

If you have any questions, you may call Taylor Vinson of this Office (202-366-5263).

Sincerely,
Frank Seales, Jr.
Chief Counsel
ref:108
d.6/3/98