Interpretation ID: 2858yy
President
MidAmerica Design Service
10206 Lima Road
Ft. Wayne, IN 46618
Dear Mr. Brown:
This is in reply to your letter of February 8, l99l, to the attention of Taylor Vinson of this Office. Your company has been asked to "develop a high mounted stop light and turn signal to be installed into the door of over the road trailers." You have not found a reference in Standard No. l08 to such a lamp, and you have concluded that, as long as you add to the trailer's existing lamps without eliminating any of its lighting devices that are standard equipment, you will be in compliance. You have asked us for our opinion on this matter.
You are correct that the requirement for a center high mounted stop lamp does not extend to trailers. Moreover, trailers are not included in the agency's pending rulemaking to extend the requirements to vehicles other than passenger cars. Although your design appears to combine the stop lamp and turn signal, a combination prohibited for passenger cars, you are under no Federal legal obligation to design a center high mounted stop lamp for trailers that complies with Standard No. l08.
As the lamp is not intended to replace original equipment required by Standard No. l08, it is permissible under section S5.1.3 of the standard as long as it does not impair the effectiveness of the lighting equipment that the standard requires. The judgment of whether impairment exists is initially that of the trailer manufacturer, who certifies compliance with all applicable Federal motor vehicle safety standards. If that decision appears clearly erroneous, NHTSA will review it and inform the manufacturer accordingly.
Assuming that the trailers for which the lamp is intended have an overall width of 80 inches or more, your lamp would be mounted in closest proximity to the three-unit identification lamp cluster, which Table II of Standard No. 108 requires to be located "as close as practicable to the top of the vehicle." Identification lamps indicate to following drivers the presence of a large vehicle in the roadway ahead. It is possible that an activated center stop lamp or adjacent turn signal could mask the light from these lamps. However, these trailers are also equipped with clearance lamps, which serve the same purpose of identifying a large vehicle. Thus, it would appear that your device would not impair the effectiveness of the identification lamps within the prohibition of section S5.1.3.
We assume that the turn signal portion of the lamp is a supplement to others on the trailer that are located to comply with the 83-inch maximum mounting height imposed by Table II.
I hope that this is responsive to your concern.
Sincerely,
Paul Jackson Rice Chief Counsel
ref:l08 d:3/7/9l