Mr. Jay Reese
Engineering Manager
Fontaine Specialized
P.O. Box 289
5398 U. S. Highway 11
Springville, AL 35146

Dear Mr. Reese:

This responds to your letter requesting an interpretation of whether four different trailers your company manufactures would be excluded from the National Highway Traffic Safety Administration's (NHTSA) recent rear impact protection (underride guard) regulations. In some cases they are excluded, and in others they are not and a guard would be required. Each trailer design is addressed separately below, with reference to the drawings you enclosed.

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 categories that are relevant for the purposes of this letter are wheels back vehicles, low chassis vehicles and special purpose vehicles.

Design 1: Drawing #BTS-5104 Flatbed

You believe that this vehicle meets the description of an excluded wheels-back vehicle. Wheels-back vehicles are excluded by S3 of Standard No. 224, Rear impact protection. The term is defined in S4 as a "trailer or semitrailer whose rearmost axle is permanently fixed and is located such that the rearmost surface of [the tire] on that axle is not more than 305 mm forward of the transverse vertical plane tangent to the rear extremity of the vehicle."

The drawing you enclosed of the trailer your company manufactures shows that the rear surface of the tires on that axle is within 305 mm of the rear extremity. Assuming the axle is "permanently fixed," this is a wheels back vehicle, and no guard is required.

Design 2: Drawing BTS-4748 Hydraulically operated dovetail with flipunder approach plate

You believe this flatbed trailer meets the definition of a special purpose vehicle. The vehicle has an 8 foot long tail section that tilts down at a 15 degree angle to permit loading of wheeled vehicles. At the rear of the section is depicted a triangular full width approach plate that, during loading, extends farther rearward and downward, bridging the gap between the tail section and the ground. Its purpose is to allow construction equipment to transition from the ground up onto the bed without encountering the "bump" of the edge of the tailpiece. During transit, this approach plate folds under the tail section and fits into an indentation in the bottom of the chassis. The forwardmost edge of the plate locks into position on the bottom of the chassis. In this position, the lower surface of the approach plate is 22 inches above the ground, and the rear face of the vehicle presents a vertical surface from 22 to 37 inches above the ground.

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) Again, the approach plate is the only part of your trailer that, while the vehicle is in transit, resides in the area that could be occupied be the rear underride guard. Therefore, the approach plate would have to be considered work-performing equipment for the trailer to be excluded.

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, 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. Approach plates do not perform work in this sense because they merely form a ramp between the ground and the vehicle driving onto the tilt bed.(2) Therefore, the approach plate is not work-performing equipment and the vehicle does not meet the definition of a special purpose vehicle.

We now turn to the question of whether your trailer is excluded as a low chassis vehicle. Low chassis vehicles are 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. The only part of your vehicle that may meet these configuration requirements is the rear edge of the folded approach plate itself, so the question becomes whether the approach plate is considered to be part of the "chassis" of the vehicle. 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 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. Moveable components may "lock" into the frame structure sufficiently that they are integral with other frame members-in this situation NHTSA may consider the combined components to be one frame unit. However, the agency also looks at the purpose and function of the structural member in supporting the trailer and its load.

Applying these principles to your approach plate, we conclude that it is part of the chassis. The folded approach plate conforms with the outline of the underside of the trailer bed, maintaining a constant bed thickness and helping to define the outline of the bed. Your approach plate is hinged along the entire rear of the trailer and, when folded, locks at its forward edge into a place fitted for it on the underside of the chassis. NHTSA considers the approach plate on your trailer to be "locked" into the frame of the vehicle sufficiently that it is considered integral with it, as one unit, and therefore a part of the frame structure. By contributing to the structural integrity of these frame members, NHTSA considers the approach plate to be supporting load. Therefore, the approach plate is part of the chassis, and the trailer is a low chassis vehicle, excluded from the underride guard requirements.

Design 3: Drawing #BTS 5110 Fixed dovetail with flipover approach plate

This trailer is similar to design 2, except that the downward-tilted dovetail section is not hydraulically operated, but attaches rigidly to the flatbed. The approach plates on this design are not full-width, and they swing up instead of down and lie on top of the dovetail when the vehicle is in motion. The rear face of the dovetail itself appears to meet the configuration requirements of S5.1.1 through 5.1.3.

NHTSA considers the dovetail section to be an integral extension of the main chassis frame members, and therefore the vehicle is excluded as a low chassis vehicle, according to the analysis in Design 2.

Design 4: Drawing BTS-2844 Pusher bumper

This vehicle, which you state is for off-road use, is a flatbed trailer with a lower chassis surface that is 31 inches above the ground. There is a "pusher bumper" cantilevered rearward from the rear underside of the trailer. It extends slightly behind the rear of the chassis and its lower surface is 17 inches from the ground. The pusher bumper is used to push the vehicle out of the soft ground in the oilfields. Your drawing notes that "pusher bumper guard assy supplied by customer." You stated that this trailer falls under the special purpose vehicle exclusion, meaning that you regard the pusher bumper as work-performing equipment.

Your questions raises two main issues: (1) whether the bumper is "work-performing" equipment, and (2) whether the "off-road" nature of your trailer excludes it from our definition of a "motor vehicle." Both of these issues are addressed below.

The pusher bumper is not work-performing equipment. As explained in the above discussion of Design 2, "work-performing"equipment must actively perform its function, and that the function must involve exerting force or moving something else. Pusher bumpers do not themselves actively exert force, but are instead passively pushed against by other equipment. Therefore, the pusher bumper is not work-performing equipment and the vehicle does not meet the definition of a special purpose vehicle. In fact, it appears that you currently consider the pusher bumper to be an underride guard. Your diagram refers to it as a "guard assy" and it appears to meet the configuration requirements for an underride guard.

Many underride guards may perform passive pushing or holding functions on occasion. For example, many trailers use their guards to secure the trailer at a loading dock using a dock locking device that holds the underride guard. When performing this function, these guards are subjected to forces in the forward-aft direction, although the forces may be less than a pusher bumper experiences. To say that all these guards are work-performing equipment would mean that many, if not most, standard van-type trailers would be excluded; clearly not what the agency intended by its special purpose vehicle exclusion.

Your diagram stated that the pusher bumper is "supplied by" the customer. Regardless of who supplies it, you, as the manufacturer of the vehicle, are responsible for installing a device that will enable you to certify that your trailer complies with Standards No. 223 and 224.(3)

You state that "the trailer is for off-road use in the oil field business." This raises the possibility that it is not a motor vehicle subject to our laws. NHTSA's statute defines the term "motor vehicle" as:

[A] vehicle driven or drawn by mechanical power manufactured primarily for use on the public streets, roads, and highways, but does not include a vehicle operated only on a rail line. 49 USC  30102(a)(6).

Whether NHTSA considers a piece of oilfield equipment to be a motor vehicle depends on its use. In the past, we have concluded that this statutory definition does not encompass mobile construction equipment, such as cranes and scrapers, which use the highway only to move between job sites and which typically spend extended periods of time at a single job site. In such cases, the on-road use of the equipment is merely incidental and is not the primary purpose for which they were manufactured. Other construction vehicles, such as dump trucks, frequently use the highway going to and from job sites, and stay at a job site for only a limited time. Such vehicles are considered motor vehicles, since the on-highway use is more than "incidental."

If the trailers are specially designed for use in the oilfields and their use of the roads is infrequent and incidental to their primary mission in the oilfield, then they are not "motor vehicles" within the meaning of the statutory definition and our regulations would not apply to them. However, we are unable to make that determination based on the very few statements in your letter.

If your Design 4 trailer is not excluded, 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 submittal.

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 555, 512

1. Note that this definition, as quoted, reflects an amendment made in response to petitions for reconsideration of the final rule. An unnecessary reference to pipe equipment containing hazardous materials was eliminated. See 63 F.R. 3654 (January 26, 1998).

2. To the extent that this interpretation is inconsistent with interpretation letters to Mr. Thomas M. Joyce and Mr. R. H. Anderson of Landoll Corporation, interpreting the frame rails of tilt bed trailers as work-performing equipment, those prior interpretations are superceded. The basic answer in those letters did not depend on this point, and the analysis in this letter is more thorough.

3. NHTSA's regulations do not control modifications that vehicle owners make to their own vehicles. However, the Federal Highway Administration's regulations may require compliant guards to be maintained after the vehicle is sold.