Interpretation ID: nht93-7.37

DATE: October 22, 1993

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Thomas G. Cehelnik -- Ph.D., Accutron T.C.S., Inc.

TITLE: None

ATTACHMT: Attached to letter dated 1/25/80 from Stephen P. Wood to Larry S. Snowhite (Std. 108) and letter dated 9/28/93 letter from Thomas G. Cehelnik to Office of Chief Council, NHTSA (OCC-9172)

TEXT:

We are replying to your letter of September 28, 1993, requesting information on Federal Motor Vehicle Safety Standard No. 108 (you will find the complete text of this standard at 49 CFR 571.108).

Your company has developed "a light system to indicate the deceleration of the vehicle." You have been informed that this agency is "investigating the safety of such a device," and "that lights that indicate braking must be 'steady-burning.'" The agency is not investigating deceleration warning systems, thus I am unable to provide you with "information on the status of the safety investigation" as you requested. Paragraph S5.5.10 of Standard No. 108 applies to all lamps provided as original motor vehicle equipment, and lists the lamps that may flash, such as turn signal lamps, but this list does not include stop lamps. A final catchall subparagraph (d) requires that "(a)11 other lamps shall be wired to be steady-burning," and this includes stop lamps.

You also asked "is it and will it become legal to turn on a warning or stop light that indicates the particular dynamic state of the vehicle?" and "(m)ust such a system necessarily be considered as a brake light?" We have encountered some deceleration warning systems that activate the stop lamps by means other than application of the service brake pedal. This is prohibited by paragraph S5.5.4 which states that "(t)he stop lamps on each vehicle shall be activated upon application of the service brakes." We have interpreted this as meaning that the stop lamps may be activated only by application of the service brakes, and that they may not be activated by reduced pressure on the accelerator pedal. A stop lamp can only be operated to indicate that the brake pedal has been applied for the purpose of slowing or stopping a vehicle. You may find of interest a letter of interpretation which I enclose (letter to Larry Snowhite, January 25, 1990) which expresses more fully our views on this subject.