Interpretation ID: nht74-2.41

DATE: 02/05/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Trailmobile Technical Center

TITLE: FMVSS INTERPRETATION

TEXT: In your letter of January 21, 1974, you cite the provision of Standard No. 108 under which "the height of the rear clearance lamps is optional if the identification lamps are located at the top of the trailer", and suggest that a similar option be adopted for identification lamps, i.e., that their height location "be made optional if the rear clearance lamps are located as close to the top of the closed van trailer as practical".

Clearance lamps are required by Standard No. 108 to "indicate the overall width of the vehicle . . . as near the top as practicable". The primary purpose of these lamps is to indicate the overall width of the vehicle, and the secondary purpose is to indicate the overall height. Identification lamps on the other hand are a system (three lamps with specified spacing) located "as near the top as practicable". The sole purpose of this system is to identify a vehicle as one of large size. When the widest part of a vehicle is at a point other than the highest point, such as when the fenders are separate or protrude from the body, the option in Standard No. 108 in effect allows the clearance lamps to be mounted at the widest point even though it would be practicable to mount them higher, as long as the identification lamps are mounted at the top of the vehicle, thus fulfilling the secondary function of the clearance lamps. Since the identification lamps are a system serving only the one function of identification, the clearance lamps cannot act as substitutes and the system must be mounted at the point of maximum visibility ("as close as practicable to the top of the vehicle"). To adopt your suggestion would allow a manufacturer to mount the system at the bottom of a vehicle even if it is practicable to mount them at the top, thus substantially negating the identification function the system serves. For this reason we cannot adopt the option you suggest.

Yours truly,

ATTACH.

TRAILMOBILE TECHNICAL CENTER

January 21, 1974

Richard B. Dyson, -- Assistant Chief Counsel, U.S. DEPARTMENT OF TRANSPORTATION, National Highway Traffic Safety Administration

Dear Mr. Dyson:

Thank you for your ruling on the rear identification lamps in a trailer shallow header (N40-302TV).

Although the ruling was not what we had hoped for, it did however contain the nucellus of a solution to the problem that would satisfy everyone concerned.

Today, the height of the rear clearance lamps is optional if the identification lamps are located at the top of the trailer. Obviously, the intent is to have the top of the rear of a van trailer marked by lights (but not necessarily by all of the required lamps).

To solve some of the problems that we manufacturers face, I request that the height location of the rear identification lamps be made optional if the rear clearance lamps are located as close to the top of the closed van trailer as practical.

I believe that this request is consistant with the intent of MVSS #108 and, in fact, is consistant with the requirements for open top, grain, and dump trailers.

Your prompt consideration and reply will be greatly appreciated.

Very truly yours,

Evan Hammond -- Manager - Central Engineering

cc: E. E. Lungren; R. J. Deller; J. E. Cook