Interpretation ID: nht79-2.41

DATE: 06/01/79

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Trailer Manufacturers Association

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of May 2, 1979, asking two questions with respect to Federal Motor Vehicle Safety Standard No. 108.

Your first question is "if it is permissible to locate clearance lamps up to 13 inches inboard of the outermost extremity of a boat trailer?" You have submitted a drawing approved by NHTSA in 1975, in which the center of the rear clearance lamps are within a zone extending from the edge of a truck to 13 inches inboard.

Standard No. 108 requires rear clearance lamps to be located "to indicate the overall width of the vehicle" (Table II). The zones installed on the truck drawing are at the extreme width of the vehicle at its top, and proper for the configuration shown. The widest part of a boat trailer, however, is at its fenders, but because of its configuration, clearance and identification lamps are necessarily mounted at the bottom of the vehicle rather than at its top. In this location they can be obscured by the load projecting over the rear of the trailer edge if mounted inboard of the fenders whereas outboard mounting renders this improbable. We conclude, therefore, that a mounting 13 inches inboard would not meet the requirement of Table II that clearance lamps be mounted to indicate the overall width of the vehicle.

Your second question is whether "it is permissible to combine a clearance lamp function in a tail lamp fixture if a second bulb is installed in the tail lamp which, when lit alone, satisfies the photometric requirements for the clearance lamp shown through the tail lamp lens . . . and further assuming that all tail lamp photometric requirements are met when the tail lamp bulb alone is lit and when both lamps are lit."

The answer is no. Paragraph S4.4.1 clearly specifies that "no clearance lamp may be combined optically with any tail lamp . . . ." The combination lamp you describe would appear to create an optical combination when both bulbs are lit.

I hope this answers your questions.

SINCERELY,

Trailer Manufacturers association

May 2, 1979

Frank A. Berndt Acting Chief Counsel U.S. Dept. of Transportation National Highway Traffic Safety Administration

Dear Mr. Berndt:

Recently the enclosed information came to our attention where apparently since 1975, an interpretation has existed that the clearance lamps on commercial highway trailers may be up to 13 inches inboard of the outermost extremity of a trailer.

Boat trailer manufacturers would like to take advantage of this same interpretation which would allow clearance lamps to be mounted directly to trailer frame siderails where both the lamp and wiring harness would be better protected than mounted to projecting fenders that owners invariably use as steps. These fenders do not project more than 13 inches, and are normally well forward of the rear of the trailer.

Please advise us if it is permissible to locate clearance lamps up to 13 inches inboard of the outermost extremity of a boat trailer.

A second question is if it is permissible to combine a clearance lamp function in a tail lamp fixture if a second bulb is installed in the tail lamp which, when lit alone, satisfies the photometric requirements for the clearance lamp shown through the tail lamp lens --- and further assuming that all tail lamp photometric requirements are met when the tail lamp bulb alone is lit and when both bulbs are lit.

Director of Engineering

Donald I. Reed

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