Mr. Donald W. Vierimaa
Vice President-Engineering
Truck Trailer Manufacturers Associations
1020 Princess St.
Alexandria, VA 22314

Dear Mr. Vierimaa:

This responds to your letter of June 1, 1994, requesting an interpretation of Motor Vehicle Safety Standard No. 108.

You have asked whether the term "underride protection device" as used in S5. in Standard No. 108 "only include the device yet to be required by NHTSA or would it include the device described in TTMA RP No. 92?"

At present, the term "rear underride protection device" as used in Standard No. 108 means the common "ICC bumper" described by the Federal Highway Administration in 49 CFR 393.86, or a similar device that the manufacturer of a trailer has provided regardless of whether it is required by 49 CFR 393.86. Thus, it presently includes the device described in TTMA RP No. 92.

You have informed us that some manufacturers are installing guards with round cross sections, and some with square cross sections rotated 45 degrees which results in a "diamond" shape orientation. In addition, on some trash trailers, a curved hook grabs and holds the round cross section guard while trash is loaded into the trailers. You have asked whether a 38 mm wide retroreflective strip of sheeting applied to these guards will comply with Standard No. 108.

S5. of Standard No. 108 specifies only that the strip shall be applied "across the full width of the horizontal member of the rear underride protection device." Although the reflective material is certified by its manufacturer for photometric conformance in the vertical position, Standard No. 108 has not been interpreted to require structural changes in trailers for the sole purpose of enhancing the conspicuity installation. The agency's decision to avoid exceptions for trailers with unusual configurations was based on the expectation that manufacturers would use

their available structures for conspicuity material, rather than re-engineer them. Thus, we believe that the application of 38 mm wide sheeting to either of these guards would comply with S5.


John Womack Acting Chief Counsel

ref:108 d:7/14/94