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Interpretation ID: 22036.ztv



    Mr. Rodney Ehrlich
    V.P. Engineering
    Wabash National Corporation
    P.O. Box 6129
    Lafayette, IN 47903



    Dear Mr. Ehrlich:

    This is in reply to your three letters of August 8, 2000, asking for interpretations of Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices and Associated Equipment.

    1.   "Front Clearance Lamp Interpretation for van trailers over 80" wide"

    You would like to use a combination front clearance and side marker lamp that would be mounted on the side of a van trailer at the top. You relate that it will be "recessed into the top rail, as far forward as practicable and still protected" from damage from tree limbs. You reference S5.3.1.1.1 of Standard No. 108 and express your belief that "the alternate mounting is permitted whereby the front inboard 45-degree requirement can be waived if the lamp is mounted for increased protection."

    You are correct. Table II requires clearance lamps to be mounted "on the front." However, S5.3.1.1.1 specifies in pertinent part that "clearance lamps may be located at a location other than on the front . . . for protection from damage during normal operation of the vehicle, and at such a location they need not meet the photometric output at any test point that is 45 degrees inboard" (they are, however, required to meet all other test points specified). We note that the location you describe on a van trailer would also appear to meet the other requirements for clearance lamps, that they be located to indicate the overall width of the vehicle and as close to the top as practicable.

    2.   "Sources of Stop Lamp Activation"

    3.   "Can Stop Lamps be activated upon actuation of the trailer emergency braking system"

    You have asked whether means other than application of the service brakes may be used to activate the stop lamps on a semi trailer. You point out that "today's ABS (antilock braking system) can be used to sense any deceleration rate and thus be used to apply the stop lamps in all braking' situations." You also point out that "another form of braking is the emergency brake that currently does not activate the stop lamps when applied," and ask whether the emergency brake system could be used for this purpose.

    Your questions are similar to those we addressed recently in letters of May 26, 2000, to Eugene Farber and C. Thomas Terry, copies enclosed. Mr. Farber had asked whether it was permissible to illuminate the stop lamps when the brakes are automatically applied. We replied that when the specific purpose of a brake application is to diminish vehicle speed, the stop lamps must be illuminated. Mr. Farber had also asked whether it was permissible to illuminate the stop lamps when other mechanisms such as transmission downshifting or engine retarders are used to achieve vehicle decelerations in excess of the normally achievable coast-down deceleration. We replied that it was permissible to illuminate the stop lamps, but not required. Our letter to Mr. Farber references a letter of April 10, 1992, to Lance Watt on the same subject, and I am enclosing a copy of that as well.

    You would like to install a trailer-mounted pressure switch that would activate the stop lamps when the emergency brake is activated and "significant deceleration of the vehicle can occur." As you will understand from our previous interpretations, it is permissible for the stop lamps to be activated upon activation of the trailer emergency braking system. You will note that the letter to Mr. Terry refers to his petition for an amendment to Standard No. 108. Mr. Terry petitioned for rulemaking to provide for automatic activation of the stop lamps when a certain rate of deceleration is reached. After review, the agency granted this petition in mid-September. As provided by 49 CFR 552.9(a), the agency will commence a rulemaking proceeding in accordance with applicable NHTSA and statutory procedures.

    If you have any questions, you may refer them to Taylor Vinson of this Office (202-366-5263).

    Sincerely,

    Frank Seales, Jr.
    Chief Counsel

    Enclosures

    ref:108
    d.9/29/00