Interpretation ID: 17799-2.pja

Mr. Michael E. Kastner
Director of Government Relations
National Truck Equipment Association (NTEA)
1350 New York Avenue, NW
Suite 800
Washington, DC 20005-4797

Dear Mr. Kastner:

This responds to your letter requesting a meeting on the National Highway Traffic Safety Administration's (NHTSA's) rear impact protection (underride guard) regulations. In a subsequent telephone conversation with Paul Atelsek on my staff, you stated that your intention was to get an interpretation of the underride standards, and that a meeting was not necessary. Specifically, you would like an explanation of the definition of the area that could be occupied by the horizontal member of the underride guard for purposes of determining whether a trailer meets the definition of an excluded special purpose vehicle. The issues you raise are addressed below.

A brief review of the rule and the salient points of your letter is appropriate to set the background for our reply. As you know, 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). You state that trailer manufacturers and end users, such as fleet managers, have interpreted our regulations as requiring underride guards on trailers and semitrailers equipped with equipment such as liftgates that is incompatible with the underride guards. End-users have reported to NTEA members a concern that underride guards could create work-related safety hazards in the form of "pinch points" between the guard and the equipment.

Concerns about certain incompatible equipment led NHTSA to exclude "special purpose vehicles" from the requirements of the standard. The main problem you cite with the exclusion of special purpose vehicles is confusion regarding the definition of these vehicles. A special purpose vehicle is defined in S4 of Federal Motor Vehicle Safety 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."⁽¹⁾ You observe that "the area that could be occupied by the horizontal member of the rear underride guard," (the "guard zone") determines the area within which the work-performing equipment would have to be located to be considered a special purpose vehicle. The remainder of your letter attempts to derive the boundaries of the guard zone. You conclude that the guard zone may be as high as the bottom of the vehicle body, as low as the ground, as wide laterally as the vehicle, and as deep, longitudinally (your letter refers to this dimension as width), as 12 inches forward from the rear extremity, plus the longitudinal width of the guard itself. You further conclude that if any work-performing equipment is mounted in the guard zone, the vehicle is excluded regardless of when and how the equipment is used.

Your understanding is generally correct regarding the boundaries of the guard zone. S5.1.2 of Standard No. 224 requires that the bottom edge of the guard be "no more than" 255 mm from the ground. The preamble to the January 1996 final rule explicitly stated that NHTSA was not setting a minimum guard height: "guards may be mounted with less than the maximum allowable ground clearance" (61 FR 2018. See also 63 FR 3657-58, denying a petition for reconsideration to set a lower limit on guard height). Therefore, the bottom of the horizontal member could theoretically be as low as the ground, although as a practical matter, such a guard would strike the ground every time the trailer hit a bump. S5.1 of Standard No. 223 requires the horizontal member of the guard to have a vertical height of "at least" 100 mm, or 4 inches. The agency in the final rule also explicitly stated "that 100 mm (4 in) is only a minimum height" (61 FR 2012). Since there is no maximum height, the top of the horizontal member could extend upward to the trailer bed. S5.1.1 of Standard No. 224 specifies a maximum lateral extension of the horizontal member as the side extremities of the vehicle. So the side extremities, as they are defined in S4 of Standard No. 224, constitute the outermost boundaries of the guard zone.

As you suggested in your letter, we interpret the rearward boundary of the guard zone to be the transverse vertical plane tangent to the rear extremity of the vehicle, and the forward boundary of the guard zone to be the transverse vertical plane 305 mm (12 inches) forward of that plane. You are correct in saying that the horizontal member of the guard must have some longitudinal thickness in order to meet the strength requirements of the standard, and that this thickness might in some installed guard designs project forward of the plane 305 mm forward of the rear extremity if the rear face of the guard is positioned tangent to that plane. You conclude that the forwardmost edge of the guard zone is equal to the 12 inches forward of the rear extremity, plus some undefined guard thickness. However, NHTSA intended to have the forward boundary of the guard zone at the plane 305 mm forward from the rear extremity, "as defined by" the configuration requirements, rather than at some undefined point in front of that. Although the regulation could be clearer, that is the most reasonable interpretation. The guard zone, as explained in this letter, should result in most tuckunder liftgate designs being excluded. The flexibility to locate a guard up to a foot forward of the rear extremity can also be used to avoid creating the pinch zones that some trailer operators are concerned about.

Your understanding is incorrect regarding when the work-performing equipment has to be in the guard zone and how the equipment is used. When you quoted the definition of special purpose vehicle, you omitted the qualifying words "while in transit," and concluded that work-performing equipment in the guard zone makes a vehicle excluded "regardless of when and how that equipment is used." NHTSA has made it clear in a number of its past interpretations that the work-performing equipment has to reside in or pass through the guard zone (though not necessarily perform its function) while the vehicle is in transit. See, e.g., May 22, 1998 interpretation to Ms. Jeanne Isbill of Tarasport Trailers. Moreover, not all equipment is considered work-performing equipment. These same interpretations make clear that 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. Liftgates of all kinds are considered work-performing equipment.

The agency wants to be flexible about guard positioning, consistent with safety. NHTSA specified limited parameters of the configuration of the guard, because every additional requirement ultimately restricts the design capabilities of manufacturers. This flexibility was provided in order to help manufacturers that are actually installing guards. We have seen manufacturers use this flexibility to engineer innovative guard designs to adjust for their special requirements. Some manufacturers have even gone beyond what is required. For example, some manufacturers of trailers that are excluded due to tuckunder liftgates have begun to voluntarily integrate structural members into their liftgates which they test and certify as underride guards.

NHTSA has received a petition for rulemaking from Thieman Tailgates, Inc., to amend the standard to address issues similar to those raised in your letter. The petition asks the agency to change the definition of special purpose vehicle to clarify the boundaries of the guard zone. It also asks NHTSA to exclude vehicles with rear mounted liftgates that reside in or pass through the guard zone, without regard to whether the vehicle is in transit. The issues you raised in your letter, as well as any subsequent comments you make on such a rulemaking, would be considered in any rulemaking that we might undertake in response to the petition.

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.

Sincerely,
Frank Seales, Jr.
Chief Counsel
d.9/9/98
ref:223#224

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).