Interpretation ID: 20576.ztv

Mr. Michael Lafon
Fleet Manager
Lincoln County Fleet Services
410 N.E. Harney Street
Newport, OR 97365

Dear Mr. Lafon:

This is in reply to your FAX of August 27, 1999, asking for an interpretation of the rear lighting requirements of Federal Motor Vehicle Safety Standard No. 108 with respect to the drawing you enclosed of a dump body.

This drawing depicts, first, two red clearance lamps (not identification lamps as you stated) mounted on the sides and at the top of the dump body. This aspect of your lighting scheme meets the requirements of Table II of Standard No. 108 that clearance lamps be mounted so as to indicate the overall width of the vehicle, and as near the top as practicable.

We note also that the three red identification lamps are mounted below the dump body, on 12-inch centers. You relate that the requirement that identification lamps be located as close as practicable to the top of the vehicle (as required by Table II) "has been a tough one for dump trucks to fully meet because of no practical place to mount these lamps up high," and that "to meet the highest practicable point of the requirement, these lamps have been traditionally mounted on the truck's rear frame cross member." You are correct that this is an acceptable location for the three identification lamps for trucks having dump bodies with rear full width/full height dumb gates.

You may be aware that we issued an interpretive rule on identification/clearance lamp location in April of this year, but it was addressed to trucks and trailers with rear doors and headers abovethem. Because your dump body has no header above the rear gate, this interpretive rule is not applicable to it. Further, the 12-inch spacing of your vehicle's identification lamps is in accordance with the requirements of Table II.

Below the clearance lamps, on each side, are two identical lamps mounted one over the other. These, plus the outer lamps of the identification lamp cluster mounted beneath the dump body, are intended to comprise the tail and turn signal lamp system. In addition, the three identification lamps would be activated when the brakes were applied. This would provide a six-lamp taillamp system, a system of three turn signals per side, and a seven-lamp stop lamp system. You point out that Standard No. 108 does not prohibit combining the identification lamp system with other lamps.

You are correct that S5.4 does not prohibit the lighting scheme you propose. However, in this instance the controlling authority is S5.1.3: "No additional lamp, reflective device or other motor vehicle equipment shall be installed that impairs the effectiveness of lighting equipment required by this standard." Intuitively, it may seem to you that providing additional stop lamp, turn signal, and taillamp functions can only enhance motor vehicle safety. However, we are convinced that our current standardized approach to motor vehicle lighting has positive safety benefits by virtue of its broad public and international acceptance, and that lighting equipment that is required by Standard No. 108 for a specific purpose ought not to be used for a different purpose. A driver, when confronted with a signal, must not be confused and must react to it as quickly as possible. The use of the outer lamps of the identification lamp cluster as supplementary turn signals, carry the potential for confusion and hence impairment of the lamps that are intended as the turn signal lamps required by Standard No. 108 because they are closer to the vertical centerline of the dump body than its outermost edges where the turn signal lamps are properly located. We therefore believe that this aspect of your lighting scheme is precluded by S5.1.3.

We note that a similar distance separates the identification lamps from the primary stop lamps. We believe that the simultaneous activation of the four primary stop lamps located as far apart as practicable on the truck body, and the three low-mounted identification lamps mounted on the frame member under the truck body and used as supplementary stop lamps may have a similar distracting effect; the public is not used to seeing a change of intensity in identification lamps mounted in that location. Therefore, this aspect of your lighting scheme is also precluded by S5.1.3. However, we have permitted identification lamps mounted at or near the top of a wide vehicle to serve as auxiliary stop lamps on the theory that the public is now conditioned to seeing high-mounted stop lamp arrays on many narrower motor vehicles and would perceive an increase in intensity of identification lamps as indicating that the brakes had been applied.

We would also like to remind you that, in mounting lamps on the dump body, the stop, turn, and taillamps must be located within the height limit specified in Table II of Standard No. 108. You did not mention the two required rear facing red reflex reflectors required by Table I. These also must be located with the height and width requirements of Table II.

We appreciate your writing us. If you have questions, you may call Taylor Vinson again (202-366-5263).

Sincerely,
Frank Seales, Jr.
Chief Counsel
ref:108
d.10/26/99