Interpretation ID: nht91-3.51

DATE: May 14, 1991

FROM: Norman H. Dankert

TO: Taylor Vinson -- Legal Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 6-3-91 from Paul Jackson Rice to Norman H. Dankert (A37; Std. 108; VSA 108(a)(2)(A))

TEXT:

This letter is a request for an interpretation of law. We have a newly issued patent # 4,922,225 that relates to the high-mounted stoplamp. The device covered by this patent offers several different operations for this light. In question here is the one dealing with the input from the service brakes to the high-mounted stoplamp.

Our device never activates the stoplamp directly. A sensor that responds to the movement of the accelerator pedal serves to maintain the activation initiated by the brake pedal until the accelerator pedal is depressed, regardless of any speed. This effect removes the error in the present method of signaling.

The present stoplamp sends three messages: (1) when the lamp is activated during normal driving conditions, the vehicle is impeding the flow of traffic. (2) when the lamp is activated on a steep decline, the driver is braking to controll his speed. This control could impede traffic flow. (3) when the lamp is off, the vehicle has joined the flow of traffic.

The discrepancy in the present signaling system occurs when the lamp if off. When the lamp is off, the driver is not always joining the flow of traffic. This discrepancy is no hazard if the following driver has good visibility and is following at the proper number of car lengths. However, on the expressways where drivers seldom follow at the proper number of car lengths, as soon as the lamp goes off the drivers may accelerate. This is why in Chicago, 56% of automobile accidents were rear-end collisions, 72% of which happened on dry pavement, and 62% on clear days.

Our system, with its sensors and circuitry, serves to enhance the existing signaling system to the degree necessary to eliminate error. It in no way inhibits or changes the meaning of the present 3rd brake light. It changes no circuitry; and if it becomes inoperative, it reverts back to the 3rd brake light system.

It appears that this manner of operation conforms to the wording of the regulation governing the high-mounted stoplamp. In # 571.108, S4.5.4, it states: "The high-mounted stoplamp on each passenger car shall be activated only upon application of the service brakes."