Interpretation ID: nht95-7.16

TYPE: INTERPRETATION-NHTSA

DATE: October 10, 1995

FROM: Edward Mansell -- Chief Engineer, Polar Tank Trailer, Inc.

TO: Philip R. Recht -- Chief Counsel, NHTSA

TITLE: NONE

ATTACHMT: ATTACHED TO 12/1/95 LETTER FROM Sanuel J. Dubbin to Edward Mansell (Redbook 2; Std. 108)

TEXT: Dear Mr. Recht,

We are requesting and interpretation of the language included in Federal Motor Vehicle Safety Standard No. 108 Lamps, reflective Devices and Associated Equipment, paragraph S5.7 Conspicuit Systems.

The NHTSA has made it clear that the exact location and configuration of conspicuity sheeting is subject to variation based on the practicability of installation. Our request involves the practicability of installation of conspicuity sheeting on the rear of some Food Grade Tank Trailers (FGTTs).

Paragraph S5.7.1.4.1(a) calls for sheeting to be placed across the full width of the trailer as close as practicable to 1.25 meters above the road surface. For many tank trailers the rear bumper, located approximately 0.5 m above the road surface, is the closest practicable location for installation of conspicuity sheeting. For some FGTTs, however, rear-mounted load/unload ports, pumps and valves are located directly above the center portion of the rear bumper.

Conspicuity sheeting affixed to a bumper under the load/unload ports is subjected to repeat exposure to hot water as run off from wash downs cascades over the sheeting. Typically this area is washed at least once per day with water up to 200 degrees F.

This repeated exposure to hot water degrades the conspicuity sheeting. Modes of failure include: loss of red coloring; delamination; loss of brightness; bubbling; cracking; and loss of adhesion. The deleterious effects of this exposure is evident regardless of the manufacturer of the sheeting. Analysis shows that sheeting applied to the rear of trailers with designs which do not result in the cascade of hot water over the sheeting do not experience these problems.

P2

We interpret paragraph S5.7.1.4.1(a) to allow, that since installation of sheeting in a location subject to frequent hot water run off is not practicable, in the case of FGTTs with designs which results in water cascading from the load/unload area over the center fo the rear bumper, the sheeting may be applied from the extreme ends of the bumper to points no more than 6 inches (150mm) to the left or right of the area directly below the load/unload area. Further, for FGTTs which use a cabinet to enclose the load/unload area, conspicuity sheeting should be mounted on the cabinet doors to augment the sheeting on the bumper.

Otherwise, the center section of the sheeting should be located on the tank, above the load/unload area.

We believe that this proposal meets the intent of Standard 108 by delineating the rear of FGTTs without requiring manufacturers to redesign trailers to redirect the flow of wash water. We look forward to your interpretation of the Standard and await your reply.