Mr. Jeffrey Echt
President, Saline Electronics, Inc.
13379 Michael Road
Highland, IL 62249

Dear Mr. Echt:

We have received your letter of March 10, 1995, asking whether it is permissible under Standard No. 108 to use the hazard warning lamps as a deceleration warning system.

Paragraph S5.5.10(a) states that "Turn signal lamps, hazard warning signal lamps, and school bus warning lamps shall be wired to flash." With this in mind, "and the fact that hazard warning indicators are commonly used to warn high-speed trailing traffic that a leading vehicle or vehicles are moving slowly or stopped", you have asked:

"1. Would a device which automatically activated a vehicle's hazard warning system at the onset of high, braking induced deceleration and deactivated the hazard warning system upon release of the brake pedal (following automatic activation) be permissible under FMVSS 108? This assumes that the device will not prevent activation or cause deactivation of the hazard warning system if the mandatory vehicular hazard warning signal operating unit has been activated by the driver."

Heretofore, the agency's opinion letters on deceleration warning systems have covered those that operate through lamps that are steady burning in use (to Norman H. Dankert on June 3, 1990, and to Bob Abernethy on September 7, 1990), or through original equipment lamps that are additional to those required by the standard (letter of July 30, 1993, to the Commonwealth of Virginia). In those instances, we have advised that a deceleration warning system must be steady burning in use.

Your question raises the issue of whether a flashing deceleration warning system is acceptable if it operates through original equipment lamps that are intended to flash when they are used. Flexible asked a similar question with respect to a supplementary lighting system. We advised it (letter of December 8, 1986) that simultaneous use of flashing

and steady-burning lamps have the potential for creating confusion in vehicles to the rear and impairing the effectivess of the required stop lamps within the meaning of S5.1.3 (the provision of Standard No. 108 that governs the permissibility of supplemental original lighting equipment). We believe that the same conclusion also applies to wiring the hazard warning system to operate as a high deceleration warning system as well. Thus, we do not view this system as permissible under Standard No. 108. Obviously, complying vehicles are manufactured so that it is possible for a driver to simultaneously activate the hazard warning system and stop lamp system. However, we believe that this happens infrequently, and when it does, it is a conscious choice of the operator and not of a system.

Because of the conclusion we have reached above, your second question is moot.

Sincerely,

Philip R. Recht Acting Chief Counsel ref:108 d:4/24/95