TLC #123 B 6” Inside the “Extreme Edge” -
I was told by a few NATM* Members at their last trade show, that they were told by NHTSA (indirectly or directly?) that mandated “Clearance Lights could be placed up to 6” Inboard of the Widest Point” on any over 80” Trailers they manufacture, which I questioned. I have heard of this 6” inboard allowance before; however, I never investigated where this 6” “Rule of Thumb” came from. So I took the time to search our extensive FMVSS #108 “Legal Interpretation s files” that we’ve built up over the years.
*National Association of Trailer Manufacturers
As a result, I found the attached 1997 “Legal Interpretations” sent to Donald Vierimaa from the 1997 “Chief Council” at NHTSA … John Womack. After reading it carefully … I believe this Interpretation does say 6” Inboard is better than further Inboard? for this particular Cargo Trailer case, but I believe it does not say the Widest Part can be routinely represented at 6” inside the real life Extreme Width of the vehicle.
I believe what Mr. Womack is saying here is that if there is no other practical place to locate the Forward Facing (Amber) Clearance Light on the … in question … over 80” wide Cargo Trailer … so that the Clearance lamp can truly represent the real life “Extreme Width” … then 6” Inboard makes for the best “practical sense” in this particular case because the front outboard edges of most Cargo Trailers routinely use ≈6” Radiuses for styling and for the lowering wind resistance.
However, if this Trailer had Protruding Fenders … the extreme Outboard Edge of the Fenders would represent the “Widest Part”* and the “Extreme Width”* and the “Overall Width”* … and recognize that when mounted on the Fenders, the light is mounted close to Average Traffic Eye Level, thus being very conspicuous to following and passing traffic and to nearby pedestrians as well.
*all of these terms are used by NHTSA and D.O.T. Interchangeably.
It should be obvious to all concerned that if the “Extreme Width” of a very Wide Vehicle is not clearly represented to Passing Traffic* and to nearby Pedestrians in both Forward and Rearward directions … “Clipping” or “Side Swiping” can more readily occur … after which, it’s anyone’s guess what can result from a soft or hard “Clip” or “Side Swipe”. *At near eye level height