Interpretation ID: nht73-5.31

DATE: 10/19/73

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Jordan Research Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of September 18, 1973 asking for an interpretation of Standard No. 108. You understand that "the stop lamps must light when applying the automobile brakes and/or when applying the trailer brakes individually." You tell us of a product that gives a driver "manual control of the trailer brakes [but] does not light the stop lamps in this mode."

Paragraph S4.5.4 of Standard No. 108 requires that "the stop lamps on each vehicle shall be activated upon application of the service brakes." This section of Standard No. 108 requires that stop lamps on new motor vehicles be wired in this manner. The standard does not apply after the vehicle is purchased, and thus does not prohibit a vehicle owner from modifying the wiring of his vehicle by adding the Electronic Trailer Brake Control. Such an addition, however, might be precluded under State law.