Interpretation ID: 19679.ztv

Mr. Stan R. Gornick, P. Eng.
Corporate Manager, Compliance & Recall
Orion Bus Company
P.O. Box 449
Oriskany, NY 13424

Dear Mr. Gornick:

This responds to your letter of March 2, 1999, to Taylor Vinson of this Office, requesting an interpretation of S5.5.4 of Federal Motor Vehicle Safety Standard No. 108.

You have described a "multiplexing vehicle wiring system" designed for transit buses manufactured by Orion Bus Company. Under this design, the system goes into "sleep mode" 15 minutes after the bus is "shutdown and parked." In the sleep mode, only the hazard warning lamps can operate. Remaining lamps are able to operate only when the bus is taken out of sleep mode by use of a "Master Power Switch."

S5.5 of Standard No. 108 is titled "Special wiring requirements," and establishes how certain vehicle lamps shall be wired to operate. S5.5.4 of Standard No. 108 requires that "The stop lamps on each vehicle shall be activated upon application of the service brakes." This means that stop lamps shall be wired to operate when the service brakes are applied. When a bus is in the sleep mode, depression of the brake pedal will not activate the stop lamps. You have asked if this is a noncompliance with Standard No. 108, and report that Rich Van Iderstine of the Office of Safety Performance Standards believes that it may be.

We have discussed this matter with Mr. Van Iderstine and have concluded that the multiplexing design, as you have described it, does not create a noncompliance with Standard No. 108. Service brakes are applied to slow or halt a moving vehicle. When a bus is parked and its electrical system is in the sleep mode, the service brakes serve no function. In this situation, we do not view depression of the brake pedal as an "application" of the service brakes, because depression of the pedal does not initiate a braking function. Therefore, the fact that the stop lamps do not activate when the brake pedal is depressed, when the bus is in the sleep mode, does not create a noncompliance with S5.5.4.

However, this interpretation does not extend to other situations where a vehicle may be at rest and the brake pedal is applied. For example, a driver of a vehicle stopped at a traffic signal may need to apply the service brakes to prevent inadvertent motion of the vehicle. Depression of the brake pedal in this instance initiates a braking function and therefore the stop lamps must activate, as required by S5.5.4.

If you have any questions, you may call Taylor Vinson at 202-366-5263.

Sincerely,
Frank Seales, Jr.
Chief Counsel
ref:108
d.3/19/99