Interpretation ID: aiam1389
Manager - Central Engineering
Trailmobile Technical Center
5570 Creek Road
Cincinnati
OH
45292;
Dear Mr. Hammond: In your letter of January 21, 1974, you cite the provision of Standar 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 th 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 your suggest.; Yours truly, Richard B. Dyson, Assistant Chief Counsel