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Interpretation ID: 22466



    Mr. Johnny Cathey
    Halliburton Energy Services, Inc.
    2600 South 2nd Street
    Duncan, OK 73536-0431


    Dear Mr. Cathey:

    This is in response to your letter of December 15, 2000, in which you ask whether we consider the trailer described in your letter to be a "special purpose vehicle" or a "low chassis vehicle" as defined in Federal Motor Vehicle Safety Standard No. 224, "Rear Impact Protection," and thus excluded from the requirements of Standard No. 224. Your trailer does not meet the definition of special purpose vehicle, but does meet the definition of low chassis vehicle. Thus, the trailer described in your letter is excluded from the requirements of Standard No. 224 as a low chassis vehicle.

    Special Purpose Vehicles

    A special purpose vehicle is defined in S4 of Standard No. 224 as "a trailer or semitrailer having work-performing equipment that, while the vehicle is in transit, resides in or moves through the area that could be occupied by the horizontal member of the rear underride guard, as defined by S5.1.1 through S5.1.3." You believe that your trailer meets this definition because "an extension must be welded to the trailer frame to accommodate the reel storage area." The reels located in the reel storage area "will be manually spooled and un-spooled from the rear of the trailer while parked on location." For your trailer to be excluded, the reels would have to be considered work-performing equipment and would have to reside in or move through the area that could be occupied by the horizontal member of the rear underride guard while the vehicle is in transit.

    There is no definition in the standard for "work-performing equipment." In determining the meaning of regulatory language, the first place the agency looks is the plain meaning of the words. In the context which is relevant to this safety standard, "work" is defined as "the transfer of energy from one physical system to another; especially, the transfer of energy to a body by the application of force . . . ." "Perform" is defined as "to begin and carry through to completion; do." (American Heritage Dictionary of the English Language, 1971). Taken together, the National Highway Traffic Safety Administration (NHTSA) interprets the words "work-performing" to mean that the equipment must actively perform its function, and that the function must involve exerting force or moving something. This is a long-standing position of the agency.

    The reels that will be welded to your trailer do not meet NHTSA's interpretation of "work-performing." The reels merely serve a storage function. In your letter, you state that the reels "will be manually spooled and un-spooled while the trailer is parked on location." Thus, they do not exert force or move anything by themselves. We conclude, consequently, that the reels do not perform any work, and that your trailer is not excluded as a special purpose vehicle.

    Low Chassis Vehicles

    A low chassis vehicle is defined in S4 of Standard No. 224 as "a trailer or semitrailer having a chassis that extends behind the rearmost point of the rearmost tires and a lower rear surface that meets the configuration requirements of S5.1.1 through 5.1.3 of this section." In other words, the chassis itself must satisfy the configuration requirements applicable to a guard when the vehicle is outfitted for transit. S5.1.1 through 5.1.3 require the guard to extend to within four inches of the side extremities of the vehicle, be no higher than 22 inches across the full width of the guard, and be located within 12 inches of the rear extremity of the vehicle.

    The only part of your trailer that meets these configuration requirements is the extension that will be welded to the trailer frame to accommodate the reel storage area. According to your letter, the extension extends the full width of the rear of your trailer, is 22 inches above the ground, and is located at the rear extremity of your trailer.

    Therefore, the question becomes whether the extension is considered to be part of the chassis of your trailer. Chassis is defined in S4 as "the load supporting frame structure of a motor vehicle." There are two elements to this definition that must be satisfied: "load supporting" and "frame structure."

    To be considered "load supporting," the frame structure has to support a load when the trailer is performing its function. Generally, this means that the structure would have to contribute to supporting the cargo load when the trailer is in transit.

    To be considered part of the frame structure, a structural member must be either an integral part of the overall frame structure, or be connected with other frame structural members in a way that is necessary to the structural integrity of the trailer. One factor the agency considers in deciding whether a structural member is part of the frame is its size and strength. Frame structural components often are the major structures defining the shape of the trailer. Although frame structure is not limited to the largest frame components (i.e., the frame rails for most trailers), generally frame components are substantial and have strength similar to other frame components.

    The agency also considers the purpose and function of the structural member in supporting the trailer and its load.

    Applying these principles to the extension that will be welded to your trailer, we conclude that it is part of the chassis. The extension contributes to supporting the cargo load (the reel storage area) when the trailer is in transit, so it is considered load-supporting. The extension is similar in size, and presumably in strength, to the other frame members. The extension conforms with and helps to define the outline of the trailer. Moreover, the extension is welded to the trailer frame. Thus, it is considered part of the frame structure. For these reasons, we conclude that the extension is part of the chassis and that your trailer is a low chassis vehicle excluded from the requirements of Standard No. 224.

    To ensure that this interpretation is properly construed, we wish to point out that any manufacturer of a trailer with a design that is close to the dimensional limits specified for exemption from the requirements of this standard should consider all the variables that could cause variance from the trailer's nominal design values. The Office of Vehicle Safety Compliance (OVSC) regularly conducts field inspections for possible noncompliances with Standard No. 224. Through these inspections, OVSC has discovered that some manufacturers may have failed to account for design aspects - such as adjustable suspension settings (for alignment purposes), optional tire sizes and equipment, and design tolerances - in assuming that their trailers are covered by an exemption from Standard No. 224. Manufacturers must ensure that the trailer satisfies the required dimensional limits throughout the range of tolerances and equipment options inherent in the trailer design.

    I hope you find this information useful. If you have any further questions regarding this matter, please contact Mr. Dion Casey in my office at (202) 366-2992.


    Sincerely,

    John Womack
    Acting Chief Counsel

    ref:224
    d.1/30/01