Interpretation ID: 2254y
CMI Trailer Division
P.O. Box 1985
Oklahoma City, Ok 73107
Dear Mr. Kossover:
This is in reply to your letter of December 8, l989, to Taylor Vinson of this Office. You have enclosed photographs of a semi-trailer that you are constructing, and wish to know whether the location of the rear turn signal, stop, and taillamps comply with the requirements of Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices, and Associated Equipment.
Table II of Standard No. l08 requires each of these lamps to be "on the rear". In addition, the SAE requirements for each of these lamps that are incorporated by reference into Standard No. l08 require that visibility of each lamp shall not be obstructed by any part of the vehicle throughout the photometric test angles for the lamp, unless the lamp is designed to comply with all photometric and visibility requirements with these obstructions considered. In addition, signals from lamps on both sides of the vehicle shall be visible through a horizontal angle from 45 degrees to the left to 45 degrees to the right. To be considered visible, the lamp must provide an unobstructed projected illuminated area of the outer lens surface, excluding reflex, at least 2 square inches in extent, measured at 45 degrees to the longitudinal axis of the vehicle.
The lamps on your semi-trailer are mounted 27 inches from the rear edge of the vehicle. In that position the lamps are not mounted "on the rear". Further, we question whether the 45 degree visibility requirements would be met, especially for the inboard lamps. We do not know whether the extended portion of the vehicle between the lamps is a sufficient obstruction to affect compliance with the photometric requirements. Overall, it does not appear that this design complies with Standard No. l08.
Sincerely,
Stephen P. Wood Acting Chief Counsel / ref:l08 d:l/9/90