Interpretation ID: 17022.wkm

Mr. Craig L. Nearman
Quality Control Manager
Load King
Post Office Box 427
Rose & Elm Streets
Elk Point, SD 57025

Dear Mr. Nearman:

Please pardon the delay in responding to your fax to Walter Myers of my staff in which you asked whether the dolly and booster on a heavy-haul trailer would be required to be equipped with an antilock brake system (ABS) in accordance with Federal Motor Vehicle Safety Standard (Standard) No. 121, Air brake systems (copy attached). The answer is no.

You enclosed a picture and drawings of the equipment you were referring to depicting a large trailer carrying a large earth mover. The trailer was equipped with a dolly on the front end and a booster on the back end, both presumably to help support the load on the trailer. You stated that the trailer has a gross vehicle weight rating (GVWR) of 164,920 pounds, the dolly a GVWR of 67,320 pounds and the booster a GVWR of 46,760 pounds. You stated that the trailer is excluded from the requirements of Standard No. 121 because it exceeds 120,000 pounds. You were unsure, however, about the status of the dolly and the booster.

Standard No. 121 applies to trucks, buses, and trailers equipped with air brake systems. Among other things, however, it does not apply to "any load divider dolly" (see S3(g) of Standard No. 121). "Load divider dolly" is defined in S4 as:

[A] trailer composed of a trailer chassis and one or more axles, with no solid bed, body, or container attached, and which is designed exclusively to support a portion of the load on a trailer or truck excluded from all the requirements of this standard.

It is clear from the picture and the drawings that you sent that both the front end dolly and the rear end "booster" meet the definition of "load divider dolly" and are therefore excluded from the requirements of Standard No. 121. Both are composed of a trailer chassis with no bed, body, or container attached; both have multiple axles; and both were designed exclusively to support the load on a trailer, assuming that the trailer itself is excluded from the requirements of the standard (see discussion on page 2). The wording of the definition does not restrict such support to only the front end. The support can be provided to any portion of the load, whether front or back.

A trailer is excluded from the standard if it has:

[A] GVWR of more than 120,000 pounds and whose body conforms to that described in the definition of heavy hauler trailer set forth in S4 (emphasis added).

"Heavy hauler trailer" is defined in S4 as:

[A] trailer which has one or more of the following characteristics, but which is not a container chassis trailer:

(1) Its brake lines are designed to adapt to separation or extension of the vehicle frame; or

(2) It s body consists only of a platform whose primary cargo-carrying surface is not more than 40 inches above the ground in an unloaded condition, except that it may include sides that are designed to be easily removable and a permanent "front end structure" as that term is used in 393.106 of [Title 49, CFR]. (NOTE: A copy of 49 CFR 393.106 is enclosed)

Since your trailer exceeds the 120,000 pound GVWR, it would be excluded from the provisions of Standard No. 121 if it also meets either of the characteristics of a heavy hauler trailer set forth above.

I hope this information is helpful to you. Should you have any further questions or need additional information, feel free to contact Mr. Myers of my staff at this address or at (202) 366-2992, fax (202) 366-3820.

Sincerely,
John Womack
Acting Chief Counsel
Enclosure
Ref: #121
d.4\29\98