Mr. Robert Lane

Director of Product Development

Heil Trailer International

1125 Congress Pky

P.O. Box 160

Athens, TN 37371-0160

Dear Mr. Lane:

This responds to your letter asking about Federal Motor Vehicle Safety Standard (FMVSS) No. 224, Rear impact protection. Specifically, you ask whether a pintle hook described in your letter would be considered a nonstructural protrusion for purposes of determining the rearmost point of the vehicle. Based on the information you provided, we would consider the pintle hook a nonstructural protrusion.

By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment.  Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture. NHTSA selects a sampling of new vehicles and equipment each year to determine their compliance with applicable FMVSSs.  If our testing or examination reveals an apparent noncompliance, we may require the manufacturer to remedy the noncompliance, and may initiate an enforcement proceeding if necessary to ensure that the manufacturer takes appropriate action.

Paragraph S4 of FMVSS No. 224 defines a rear extremity as:

[T]he rearmost point on a vehicle that is above a horizontal plane located 560 mm [22 inches] above the ground and below a horizontal plane located 1,900 mm [75 inches] above the ground when the vehicle is configured as specified in S5.1 of this section and when the vehicle's cargo doors, tailgate, or other permanent structures are positioned as they normally are when the vehicle is in motion. Nonstructural protrusions such as taillights, rubber bumpers, hinges and latches are excluded from the determination of the rearmost point.

According to the information provided in your letter, the lowest point of the pintle hook is situated 25 inches above the ground, and the hook extends 7.125 inches rearward from the (otherwise) rearmost point of the vehicle. The diagram included with your letter indicated the total area of the pintle hook attachment plate is approximately 50 square inches.

We note that, as we have stated in the past, merely because something is attached to the body, as opposed to the chassis, does not mean that an object is nonstructural. The definition of rear extremity refers to the rearmost point on a vehicle, not the rearmost point of the chassis, or the rearmost point of the steel structure. The attributes that the examples of nonstructural protrusions listed in this definition have in common are that they are relatively small and localized and would not have a major impact on a colliding passenger vehicle.[1]

We have previously issued several interpretations regarding rear attachments where there was a question as to whether they might be considered nonstructural. In these interpretations, several factors were considered. First, we took into account the width of the protrusion. Second, we took into account how rigid the protrusion was, as it related to the damage it could cause if it struck the occupant compartment of a vehicle in a rear impact. Finally, in two cases, we analyzed the height of the protrusion, also with regard to how likely it was to strike the occupant compartment of a vehicle.

Several letters found that the protrusion did not qualify as a nonstructural protrusion. In one letter[2] we determined that a 0.19 inch thick steel deflector plate that extended across the entire width of the trailer was part of the vehicle, and thus not a nonstructural protrusion. Similarly, we found that an 18 inch deep spreader pan, located 52.75 inches above the ground and extending the width of a trailer, was not a nonstructural protrusion,[3] noting that at that height the spreader pan could penetrate the passenger compartment of a colliding passenger vehicle. Finally, NHTSA also found that a plastic rear apron extending 27 inches from the rear of the vehicle and that wraps around the tailgate was not a nonstructural protrusion.[4] In making this determination, we noted that [i]f [the writers] flexible rear apron did not contact any metal structure of the colliding passenger vehicle but instead penetrated the windshield, it could be harmful if its lower edge struck the head or neck of the front seat occupants as they are thrown forward by the force of the crash. Copies of these letters are enclosed for your convenience.

The pintle hook you describe appears to be markedly different than the three examples above where NHTSA determined the protrusions to be structural. The three previous analyses all concerned devices that extended across the entire width of the trailer. Unlike them, the pintle hook attachment, according to your letter, only occupies 50 square inches of space on the rear of the trailer, and it appears that the part of the hook that extends outward occupies only a relatively small part of that area. Furthermore, we note that the pintle hook is located only 25 inches above the ground, which means it is unlikely that the hook would impact the occupant compartment of a passenger car directly. However, it is our understanding that a pintle hook is a rigid metal structure. Nonetheless, based on the totality of these facts, we would consider the pintle hook a nonstructural protrusion, similar to the taillights, rubber bumpers, hinges and latches listed in paragraph S4 of the standard.

If you have any further questions, please contact Ari Scott of my staff at (202) 366-2992.

Sincerely yours,

Stephen P. Wood

Acting Chief Counsel


Dated: 7/24/09

[1] See October 7, 1999 letter to Mr. Jason Backs, available at

[2] October 20, 1997 letter to Michael L. Ulsh, available at

[3] January 25, 2001 letter to Mr. Jeff Shahan, available at

[4] October 7, 1999 letter to Mr. Jason Backs, available at