Interpretation ID: 24338

Mr. Dale Dierks
Engineering Manager
Dakota Manufacturing
PO Box 1188
Mitchell, SD 57301

Dear Mr. Dierks:

This responds to your letter in which you asked whether the tilt bed trailers manufactured by Dakota Manufacturing are excluded from Federal Motor Vehicle Safety Standard No. 224, "Rear Impact Protection." As explained below, the answer is no.

According to your letter, your tilt bed trailers are flatbed trailers with bed heights ranging from 35.4 to 39.1 inches off the ground. At the rear of the bed is an approach plate that extends across the entire rear of the trailer. When the trailer bed is tilted for loading purposes, the approach plate is extended outward and bridges the gap between the trailer bed and the ground. When the trailer is in transit, the approach plate is locked in a downward position. The height of the approach plate, when it is locked in a downward position, ranges from 15.6 to 19.4 inches off the ground.

Standard No. 224 requires most trailers and semitrailers with a gross vehicle weight rating (GVWR) over 10,000 pounds to be fitted at the rear with a rear impact guard meeting the requirements of Standard No. 223, "Rear Impact Guards." However, certain kinds of vehicles are excluded. The only excluded categories that are relevant for the purposes of this letter are the low chassis vehicle and special purpose vehicle categories.

Low Chassis Vehicle

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 S5.1.3 of this section." In other words, the chassis itself must satisfy the configuration requirements applicable to a rear impact guard when the vehicle is outfitted for transit. S5.1.1 through S5.1.3 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 approach plate. As noted above, the approach plate is located at the rear extremity of your trailer, extends the full width of your trailer, and is 15.6 to 19.4 inches above the ground. Therefore, the question becomes whether the approach plate 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: "frame structure" and "load supporting."

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 we consider 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. We also consider the purpose and function of the structural member in supporting the trailer and its load.

To be considered load supporting, the frame structure must 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.

Applying these principles to your tilt bed trailer, we find that the approach plate is not part of the chassis. The approach plate does not meet the "load supporting" aspect of the chassis definition because the approach plate does not contribute to supporting cargo load. The approach plate also is not part of the frame structure of the trailer. The approach plate does not define the shape of the trailer. Instead, it hangs down from the rear end of the trailer, forming a protrusion from the outline of the trailer bed. Finally, the size and strength of the approach plate are not similar to the other frame components, and it is not considered integral with another frame member.

In consideration of these factors, we believe that the approach plate is not part of the frame structure, but an attachment. Thus, the approach plate is not part of the chassis, and your tilt bed trailers are not excluded from Standard No. 224 as low chassis vehicles.

Special Purpose Vehicle

We turn now to the question of whether your tilt bed trailers are excluded as 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 impact guard, as defined by S5.1.1 through S5.1.3." Again, the approach plate is the only part of your tilt bed trailer that, while the vehicle is in transit, resides in the area that could be occupied by the rear impact guard. Therefore, the approach plate would have to be considered work-performing equipment for your tilt bed trailer to be excluded.

There is no definition of "work-performing equipment" in Standard No. 224. The Agency has historically interpreted 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 or equipment driving onto the tilt bed. Therefore, the approach plate is not work-performing equipment, and your tilt bed trailer does not meet the definition of a special purpose vehicle.

Since your trailer does not meet the definition of an excluded category, and it has a GVWR over 10,000 pounds, it must be equipped with a rear impact guard meeting our standards. In your letter, you stated that you currently install rear impact guards on your tilt bed trailers, but that the guards have added "significant cost" to your trailers.

Another option you might consider is whether your approach plate could "be" the rear impact guard. The approach plate already appears to meet the configurational requirements for a rear impact guard. If it does not currently meet the strength and energy absorption requirements of Standard No. 223, you might be able to reinforce or otherwise modify the approach plate sufficiently so that it would pass these requirements. If you can do this, the approach plate itself could be labeled and certified as a guard under Standard No. 223.

I hope you find this information useful. If you have any further questions, please feel free to contact Dion Casey of my staff at (202) 366-2992.

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d.8/1/02