Ms. Jeanne Isbill
TarasPort Trailers, Inc.
P.O. Box 327
Sweetwater, TN 37874

Dear Ms. Isbill:

This responds to your letter requesting an interpretation of whether two trailers your company manufactures would be excluded from the National Highway Traffic Safety Administration's (NHTSA's) rear impact protection (underride guard) regulations. You enclosed photographs of two flatbed trailers with rear extenders that slide out as much as 36 inches from the rear of the chassis. In the case of one trailer, the extension is full width, meaning that the extension forms a continuous plane from one side of the trailer to the other. On the other trailer, the extensions are only on the sides, like the small shelves that slide out from office desks on either side of the chair. Although no dimensions are given, it appears from the photographs that the extenders are more than 560 mm above the ground, near the top of the trailer tires. You ask if these trailers are special purpose vehicles and, if so, whether their bumpers need to be labeled stating that they are excluded. As explained below, these trailers are not excluded special purpose vehicles, and a compliant underride guard would need to be provided.

Federal Motor Vehicle Safety Standard No. 224, Rear impact protection, requires most trailers and semitrailers weighing over 10,000 pounds to be fitted at the rear with a rear impact (underride) guard meeting the requirements of Standard No. 223, Rear impact guards (49 CFR 571.223 and 571.224, published on January 24, 1996 at 61 FR 2004). However, certain kinds of vehicles are excluded. The only excluded category that is relevant for the purposes of this letter is that of "special purpose vehicles."

A special purpose vehicle is defined in S4 of FMVSS 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."(1) S5.1.2 states that "[t]he vertical distance between the bottom edge of the horizontal member of the guard and the ground shall not exceed 560 mm at any point across the full width of the member. . . ." We can see no part of your trailer that, while the vehicle is in transit, would reside in or pass through an area described in S5.1.2.

In addition, to be a special purpose vehicle the guard area would have to be occupied or passed through by work-performing equipment. 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 else. There is no work-performing equipment at the rear of your trailers. Therefore, these vehicle do not meet the definition of a special purpose vehicle. No other exclusion applies to them, so the vehicle would have to be equipped with an underride guard meeting the requirements of 49 CFR 571.223 in order to be certified. The guard would have to be labeled as specified in S5.3 of Standard No. 223.

When deciding how to mount the guard, please keep in mind that a vehicle would have to meet the requirements of the rule in every configuration in which it can be operated on the road. Standard No. 224 does not specify the position the rear extenders would have to be in when the agency determines compliance. When a standard does not specify a particular test condition, we begin with a presumption that the requirements must be met in every test condition in which the vehicle can be operated. See, for example, NHTSA's October 2, 1990 letter to Mr. S. Kadoya of Mazda. Starting from this presumption, we look to the language of the standard and its purposes for guidance to decide whether some limitation on the test condition should be implied. We see no language that would imply a limitation. As to the purposes, with the trailer configured in the flatbed mode with its rear end at a height above 560 mm, a colliding vehicle would likely underride the trailer rear extenders. This safety concern is one that the agency considered extensively in the January 24, 1996 final rule (see 61 FR 2016-18), and it is this kind of situation the regulation was intended to prevent. Therefore, NHTSA could determine whether the vehicle complied with the rear extenders in any position they could be placed in transit.

S5.1.3 of Standard No. 224 states that the horizontal member of the guard must be as close as practicable to the rear extremity of the vehicle, but in no case farther than 305 mm from the rear extremity of the trailer. Your trailer's rear extremity with the extenders out would be the rearmost surface on the extenders themselves. To comply with S5.1.3, the rear face of the horizontal member of the guard would need to be no farther forward than 305 mm from the extenders, when the extenders are in any position in which they can be placed when in transit.

We cannot provide a specific opinions on how your trailer might be redesigned to accommodate a guard. We note, however, that the standard specifies only the guard's horizontal member position, and therefore there is a great deal of flexibility in how you attach the guard to the trailer, so long as the strength and energy absorption requirements are met. There is no requirement that the guard be suspended from the bed area. A guard attached to the extenders would move in and out with them, thus complying with the S5.1.3 no matter what position the extenders are in. However, we emphasize that it is you, as the vehicle manufacturer, who is responsible for the vehicle's compliance with the standard.

If you expect to encounter unusual difficulty redesigning your trailers, the agency would consider a petition for temporary exemption from Standard No. 224. Under one of our regulations (49 CFR Part 555), vehicle manufacturers may apply for a temporary exemption from the Federal motor vehicle safety standards. Under Sec. 555.6(a), a manufacturer whose yearly production is not more than 10,000 units may ask for an exemption of up to three years on the basis that compliance would cause it substantial economic hardship and that it has attempted in good faith to comply with the standard from which it has asked to be excused. We have enclosed a copy of Part 555 for your information. We have also enclosed a copy of our regulations relating to the protection of confidential business information. Most of the trailer manufacturers submitting petitions for temporary exemption have requested that their financial information remain confidential.

Please note Part 555 requires the agency to publish a notice in the Federal Register seeking public comment on each exemption petition before a decision can be made on such a request, and then publish a second notice either granting or denying the petition. This process normally takes three to four months from the date of submission.

If you have any further questions, please feel free to contact Paul Atelsek of my staff at this address or by telephone at (202) 366-2992.

John Womack
Acting Chief Counsel
Enclosures: Parts 512, 555

1. Note that this definition, as quoted, reflects an amendment made in response to petitions for reconsideration of the final rule. See 63 F.R. 3654 (January 26, 1998).