Interpretation ID: nht88-2.96

TYPE: INTERPRETATION-NHTSA

DATE: 08/10/88

FROM: ERIKA Z. JONES -- CHIEF COUNSEL NHTSA

TO: STEPHEN BORKOWSKI

TITLE: NONE

ATTACHMT: LETTER DATED 06/24/88 TO ERIKA Z. JONES FROM STEPHEN BORKOWSKI, OCC - 2243

TEXT: Dear Mr. Borkowski:

This is in reply to your letter of June 24, 1988, asking about the legality of your "Bimmer Dimmer Safety Stop Light Concept". The concept has as its goal to lessen the chance of rear end collisions, by governing "the intensity of brake light brightness to indicate the degree of braking being applied to a vehicle."

Federal Motor Vehicle Safety Standard No. 108 Lamps, Reflective Devices, and Associated Equipment governs the legality of your concept. SAE Standard J586c Stop Lamps, August 1970, has been incorporated by reference, and specifies appropriate photometric requirements. Paragraph S4.5.4 of Standard No. 108 requires in pertinent part that "the stoplamps on each vehicle shall be activated upon application of the service brakes". We believe that this means that the lamp shall display the intensity that is designed into it to meet the photometrics of J586c. The photometrics are expressed in terms of a minimum for each test point and while there is not a corresponding maximum for each point, there is an overall maximum for the lamp. Thus, a lamp of variab le intensity could fall below the minimum at one or more test points or exceed the overall maximum. This, of course, would result in a noncompliance with Standard No. 108.

The agency examined the problem of rear end collisions and concluded that the most appropriate way to address it was through the center highmounted stoplamp, required equipment on passenger cars manufactured on and after September 1, 1985. This is inten ded not only to reduce the incidence of rear end collisions but also their severity. We are interested in the possibility of further reductions in rear end collisions. Because your concept may be of interest to that Office, I am forwarding a copy of yo ur letter to the agency's Associate Administrator for Research and Development for such further correspondence as may be warranted. We appreciate your interest in motor vehicle safety.

Sincerely,