Vice President - Engineering
Truck Trailer Manufacturers Association
1020 Princess Street
Alexandria, VA 22314
Dear Mr. Vierimaa:
We have received your letter of April 15, 1996, asking for interpretations of Federal Motor Vehicle Safety Standard No. 108 as it relates to trailer lighting.
You have informed us of "lowbed trailers [with] narrow goosenecks that are attached to a wider load deck which may be less than 15 inches above the ground." Because Table II of Standard No. 108 requires side marker lamps on trailers whose overall width is 80 inches or more to be mounted at a height of not less than 15 inches, you have asked if the lamps may be mounted at a height of less than 15 inches if the height of the mounting location is "as high as practicable."
Your question is asked with reference to a combination clearance/front side marker lamp. As we explain below, this combination lamp cannot be used to meet the requirements of Standard No. 108 in the manner you posit.
The requirement of Standard No. 108 for front side marker lamps is that they be located "as far to the front as practicable" and, at the front, "not less than 15 inches" above the road surface. Thus, the minimum mounting height is expressed as an absolute rather than, like the horizontal location, in terms of practicability. It is our observation that the gooseneck on lowbed trailers is more than 15 inches above the road surface, and that it would be practicable to mount a side marker lamp there, thus complying with the location requirements of Table II.
You have also informed us that, on the typical lowbed trailer with a gooseneck, the combination front clearance/front side marker lamp is mounted at an angle on the front corners of the deck. The manufacturer chooses this location because "[i]f front clearance lamps were mounted on the front face of the deck directly behind the tires of the towing vehicle, they would likely be damaged by debris thrown by the towing vehicle's tires." Based upon certain NHTSA interpretations which you quoted, you asked for confirmation that a combination lamp mounted at such a location complies with Standard No. 108 "without needing to be visible at 45 degrees inboard."
Upon review, we did not find that the interpretations you quoted really provided confirmation of the interpretation that you seek. However, you also called our attention to the following:
"Clearance lamps may be mounted at a location other than on the front and rear . . . for protection from damage during normal operation of the vehicle, and at such a location they need not be visible at 45 degrees inboard." (49 CFR 571.108, S220.127.116.11.1)."
This provision (now renumbered as S18.104.22.168.1) does allow mounting clearance lamps "at a location other than on the front" if the manufacturer determines that the alternate location is needed to protect the lamp from damage during normal operation of the trailer. We believe that the lamps should also be protected from damage if the alternate location is chosen. It seems to us that mounting the clearance lamps at an angle on the front, rather than on the front involves a move of only a few inches at most, and might not provide any greater protection from road debris than mounting the clearance lamps on the front. We ask you to consider this in determining the appropriate location for the clearance lamps, keeping in mind that their primary purpose is to indicate the overall width of the trailer.
This means that a combination clearance/front side marker lamp will not meet the location requirements of Standard No. 108. A separate front side marker lamp must be provided and located on the gooseneck. A separate clearance lamp must be provided, and located in accordance with the views expressed in the preceding paragraph.
If you have any further questions you may refer them to Taylor Vinson (202) 366-5263.
Samuel J. Dubbin Chief Counsel