Interpretation ID: nht93-6.29

DATE: September 2, 1993

FROM: Donald W. Vierimaa -- Vice President-Engineering, Truck Trailer Manufacturers Association

TO: John Womack -- Acting Chief Counsel, NHTSA

COPYEE: TTMA Engineering Committee; Tank Conference Engineering Committee; The 3M Company; Reflexite

TITLE: Conspicuity

ATTACHMT: Attached to letter dated 2/7/94 from John Womack to Donald W. Vierimaa (A42; Std. 108)

TEXT:

We request three interpretations pertaining to S5.7 of FMVSS 108.

Conversion from S1 to English linear dimensions

May we consider the following nominal English dimensions equivalent for the purpose of compliance with S5.7 of FMVSS 108?

FMVSS 108 English English Citation Item Metric (actual**) (nominal)

5.7.1.3(b) Length of 300 mm 11.8 inches 12 inches red or white +/- 150 mm +/- 5.9 inches +/- 6 inches block of (150 mm (5.9 inches (6 inches sheeting to 450 mm) to 17.7 in.) to 18 inches)

5.7.1.3(d) Width of Grade 50 mm min* 1.9 inches 2 inches DOT C2 sheeting

5.7.1.3(d) Width of Grade 75 mm min* 2.9 inches 3 inches DOT C3 sheeting

5.7.1.3(d) Width of Grade 100 mm min* 3.9 inches 4 inches DOT C4 sheeting

5.7.1.4(b) Edge of white 75 mm min. 2.9 inches 3 inches sheeting to any lamp

5.7.1.4(c) Edge of red 75 mm min. 2.9 inches 3 inches sheeting to an amber lamp

5.7.1.4.1(a) Height of 1.25 m 49.2 inches 49 inches horizontal sheeting on rear

5.7.1.4.1(b) Length of 300 mm min* 11.8 inches 12 inches sheeting in upper contours of trailer

5.7.1.4.2(a) Height of 1.25 m 49.2 inches 49 inches horizontal sheeting on side of trailer

5.7.1.4.2(b) Alternative 25 mm min* 0.98 inches 1 inch width of two strips of Grade DOT C2 sheeting and their separation 25 mm max 0.98 inches 1 inch

5.7.1.5 Sheeting 3 mm min 0.118 inches 1/8 (0.125) certification inch character height

5.7.1.5 Sheeting 300 mm max 11.8 inches 12 inches certification marking separation

5.7.2.2(b) Alternative 100 mm max 3.9 inches 4 inches reflex reflector center to center separation

5.7.2.3 Reflex 3 mm min 0.118 inches 1/8 (0.125) reflector inch certification character height

* Assumed to be minimum. ** Significant decimal places for comparison.

The nominal English dimensions without underlining would appear to be acceptable conversions since they exceed the minimum metric dimensions. The nominal English dimensions underlined would, however, exceed the metric maximum dimension.

SAE J1322 JUN85, "Preferred Conversion Values for Dimensions in Lighting - Inch-Pound Units/S1," describes how English units may be converted to S1 (metric) units, but does not describe how to convert S1 units to English Units.

Vertical Location of Rear and Side Sheeting Cargo tank trailers may have a "vertical" surface only at their "belt line" which may be as high as 90 inches (2.3 m) above the ground. Retroreflective sheeting could, however, be located much closer to the ground, but for some

cargo tank trailers this may place the sheeting on non-vertical surfaces. In our comment of March 31, 1992 to Docket No. 80-9; Notice 4 we stated that "it is not clear from the proposed rulemaking as to where retroreflective material should be placed on curved surfaces of tank and some dump trailers or angled surfaces of some dump trailers."

One manufacturer of retroreflective sheeting states that "the sheeting could be applied at a maximum angle of 30 degrees to the vertical." This manufacturer reports that "An angle greater than this provides less conspicuity as defined by NHTSA."

May retroreflective sheeting be located significantly higher than 1.25 m above the road surface if there is no vertical surface lower than this height without installing structure just for the sheeting?

Upper Contour Sheeting

May the horizontal and vertical sheeting to the right and left upper contours of the trailer body required per S5.7.1.4.1(b) be of the dimensions and location shown in the enclosed figures 1 through 5?

Since a number of trailer manufacturers are presently installing conspicuity treatments in accordance with S5.7 of FMVSS 108 as standard equipment or at the request of their customers, your timely response is desirable.