Interpretation ID: nht94-1.43

TYPE: Interpretation-NHTSA

DATE: February 7, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Donald W. Vierimaa -- Vice President - Engineering, Truck Trailer Manufacturing Association

TITLE: None

ATTACHMT: Attached to letter dated 9/2/93 from Donald W. Vierimaa to John Womack (OCC-9050)

TEXT:

We have reviewed your letter of September 2, 1993, asking for three interpretations of S5.7 of Federal Motor Vehicle Safety Standard No. 108, the provisions that relate to heavy trailer conspicuity.

You have set forth the metric dimensions specified in S5.7, together with corresponding values under the headings "English (actual)," and "English (nominal)." The latter is a rounding off of the values of "English (actual)." Your first question is whet her you may consider the English (nominal) dimensions equivalent for the purpose of compliance with Standard No. 108.

We assume that you would like to provide measurements in the conventional manner to your members who may not be familiar with the metric system, as a means of assisting them to comply with the conspicuity requirements that become effective December 1, 19 93. However, the Federal motor vehicle safety standards are not expressed in equivalents, but in precise values, whether metric or conventional, and there can be no rounded "equivalences" for purposes of compliance with Standard No. 108. SAE J1322 JUN8 5 "Preferred Conversion Values for Dimensions in Lighting" which you reference has not been incorporated into Standard No. 108. In implementation of Departmental and national policy, NHTSA has begun to specify the requirements of the Federal motor vehic le safety standards using metric system values, and manufacturers are expected to learn and to comply with them.

We would also like to correct a misimpression indicated in your letter. You have placed a single asterisk by certain metric values reflecting your assumption that these are minimum values. This is incorrect; the standard expresses these values as fixed values rather than minimum ones. However, you are correct in your identification as minimum of those values that are not designated by an asterisk.

Your second question concerns the location of rear and side sheeting. You point out that cargo tank trailers may have a "vertical surface" only at their "belt line" which may be as high as 2.3 m above the ground. You ask whether retroreflective sheetin g may be located higher that 1.25 m if there is no vertical surface lower than this height "without installing structure just for the sheeting." As adopted, Standard No. 108 specified a mounting height as close as practicable to 1.25 m. However, in a n otice published on October 6, 1993, NHTSA amended the requirement to "as close as practicable to not less than 375 mm and not more than 1525 mm above the road surface." The practicability qualification allows manufacturers to choose a location for consp icuity treatment that is outside the specified

range to avoid body modifications that might otherwise be required to mount the material within the specified range.

The manufacturers of conspicuity material certify its performance as mounted on a vehicle in a vertical plane. Trailer manufacturers are expected to mount the material in a vertical plane or as close to a vertical plane as the trailer shape offers. In the case of your hypothetical tank trailer without a suitable vertical surface below the belt line of the tank, reflective material at the belt line, whether 2.3 m or higher, would be considered to have been mounted as close as practicable to the upper s pecification of the height range (1.525 m). As NHTSA observed when it adopted the original mounting height specification with its practicability provision, flexibility in the vertical location of conspicuity material is necessary for compliance of some tank trailers. However, it should not be overlooked that other types of tank trailers may have vertical surfaces on the frames, fenders, or other equipment well suited for conspicuity material.

Your third question presents five Figures and asks with respect to each whether the vertical and horizontal sheeting for the upper right and left contours, as specified by S5.7.1.4.1(b), may be of the dimensions and locations shown. This section require s application of two pairs of white strips of sheeting, each pair consisting of strips 300 mm long, applied "vertically" and "horizontally" to the contours "as close to the top of the trailer and as far apart as practicable." With respect to Figures 1 a nd 2 (van trailers), we shall assume that the horizontal strips are mounted as close to the top of the trailer as practicable. Figure 1 depicts two separate strips at right angles to each other, each 300 mm in length. This design is not in accordance w ith Standard No. 108. The side strip does not appear mounted as close to the top of the trailer as practicable, and the top strips do not appear to be mounted as far apart as practicable. While the presence of door hinges may necessitate designs simila r to Figure 1, this design, as drawn on an unobstructed surface, does not comply. To effect compliance, either the side strips should be moved upwards, or the top strips should be moved closer to the outside corners.

Figure 2 depicts two strips joined at the corners to make an inverted "L." Each leg of the "L" is 300 mm in length when measured from the outside, top to bottom, or side to side. This configuration is in accordance with S5.7.1.4.1(b).

Figures 3 and 4 present alternative conspicuity treatments for liquid tank trailers where the body is curved rather than rectangular. In Figure 3, two strips 30 mm in length intersect at an angle greater than 90 degrees. In Figure 4, a curved strip 600 mm in length follows the contour of the body. Paragraph S5.7.1.4.1(b) of Standard No. 108 requires marking the upper outer contours of the body with strips "applied horizontally and vertically to the right and left upper contours of the body ...." Howe ver, the rear contours of a tank body are rounded rather than vertical and horizontal. In view of this fact, the agency accepts the treatment shown in your Figure 3 as meeting the requirement for horizontal and vertical application. The design of Figur e 4 does not differ in any significant way, and we consider that it is equivalent.

Finally, Figure 5 depicts a dry bulk trailer with a 300 mm strip centered horizontally at the top of a round body, and two strips of the same length placed lower, at an angle slightly off of vertical, but far from the edges of the body contour. We under stand that the body of the trailer tapers to a blunt end represented by the circle upon which the horizontal conspicuity treatment is laced. As the approximately vertical strips cannot be placed on the tapering trailer body, they should be located as fa r apart as practicable, and the depicted location appears to represent that placement. Similarly, if two horizontal strips cannot be placed on the trailer body, NHTSA will not question the compliance of the vehicle based on the provision of a single, cen ter strip of retroreflective material.