Mr. Eric Reed
P.O. Box 138
Bondurant, WY 82922

Dear Mr. Reed:

This is in reply to your letter of November 18,1999. We regret the delay in responding, but as Taylor Vinson of this Office explained to you on January 27, 2000, your letter was misassigned.

With respect to S5.5.4 of Federal Motor Vehicle Safety Standard No. 108, "Lamps, Reflective Devices and Associated Equipment," you have asked whether you are correct in assuming that stop lamps must remain "activated" "as long as the service brake is applied." You comment that "the regulations do not address any duration of burn time or delay in de-activation of the stop lamps after the service brakes are released."

Standard No. 108 incorporates by reference SAE Standard J586 FEB84 "Stop Lamps for Use on Motor Vehicles Less Than 2032 mm in Overall Width" and SAE Standard J1398 MAY85 "Stop Lamps for Use on Motor Vehicles 2032 mm or More in Overall Width." Paragraph 2.1 of each of these standards defines a stop lamp in part as a lamp that indicates "the intention of the operator of a vehicle to stop or diminish speed by braking." Thus, S5.5.4 requires the stop lamps to activate when the service brakes are applied. The activation of the stop lamps at that point indicates that the driver intends to slow down or stop, and the stop lamps must remain activated as long as the service brake is applied. When the force that applies the service brakes is removed, the stop lamps are deactivated, as the operator's intent has become something other than to stop or diminish speed by braking. Continued activation of the stop lamp of any duration, in the absence of service brake application, is therefore not permitted by Standard No. 108.

You asked Mr. Vinson whether it is permissible for the hazard warning signal lamps to be automatically activated by a sensor to warn drivers approaching from the rear that their closing speed is excessive. Standard No. 108 incorporates by reference SAE Recommended Practice J910 "Vehicular Hazard Warning Signal Operating Unit," January 1966. Paragraph 1 of J910 defines the unit as "a driver controlled device which causes all turn signal lamps to flash simultaneously to indicate to the approaching drivers the presence of a vehicular hazard." An automatic activation of the hazard warning unit would not be "driver controlled" and is therefore not permitted.

Frank Seales, Jr.
Chief Counsel