Interpretation ID: nht88-3.5

TYPE: INTERPRETATION-NHTSA

DATE: 08/15/88

FROM: ERIKA Z. JONES -- CHIEF COUNSEL NHTSA

TO: LOUIS F. KLUSMEYER -- SENIOR RESEARCH SCIENTIST VEHICLE RESEARCH AND DEVELOPMENT, SOUTHWEST RESEARCH INSTITUTE

TITLE: NONE

ATTACHMT: LETTER DATED 07/11/88 TO TAYLOR VINSON FROM LOUIS F KLUSMEYER, OCC - 2275; Std. 108

TEXT: Dear Mr. Klusmeyer:

This is in reply to your letter of July 11, 1988, to Mr. Vinson of this office with reference to a "deceleration" or "pre-braking" concept.

As you presently envision the implementation of this concept, an amber lamp would be activated when the driver's foot is removed from the accelerator pedal, and would be extinguished automatically when the driver reapplies pressure to the accelerator ped al. You believe that the optimum location appears to be immediately adjacent to the center highmounted stoplamp. You believe further that this location has already been considered by NHTSA for this purpose, and ask whether it is precluded by Standard N o. 108.

Your belief is based upon the Federal Register notice of October 1983 adopting the center highmounted stoplamp, which stated that "Other types of lamps or added functions such as deceleration signals may be desirable and should be investigated." However, this was in the context of alternatives to adoption of the center lamp, and relates to the agency's statement in the same paragraph that "with additional research, more nearly optimum specifications for stoplamp configurations may be developed." Indeed, the agency made it quite clear in prohibiting combining the center lamp with any other lamp or reflector (paragraph S4.4) that no added functions were contemplated or desirable.

Under paragraph S4.4 therefore, a deceleration lamp and the center stop lamp could not be combined. S4.4 would not prohibit an amber lamp adjacent to the center lamp. However, paragraph S4.1.3 prohibits optional lighting equipment if it would impair th e effectiveness of lighting equipment required by Standard No. 108. Your letter indicates that the deceleration signal is deactivated by renewed pressure on the accelerator pedal (and not by pressure on the brake pedal) so that a following driver would be presented with both amber and red signals, creating the possibility of confusion, and hence impairment. You have not indicated whether the deceleration lamp would be steady-burning or

2 flashing, but we believe the possibility of confusion would increase were the lamp flashing. However, were the lamp to be extinguished when the brake pedal is applied (which activates the stop lamps), then the possibility of confusion would be substan tially lessened. With respect to deceleration warning systems, last year the Flxible Corporation determined that a system installed on its buses created an impairment, and hence a noncompliance with paragraph S4.1.3. The company then conducted a notific ation and remedy campaign (87V-089) as required by statute. The company concluded that its flashing amber deceleration lamps could create confusion when activated simultaneously with the red steady burning stoplamps.

I hope that this answers your question.

Sincerely,