Interpretation ID: nht74-2.20

DATE: 05/13/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: American Trailers, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your April 12, 1974, question whether a permanently attached steerable axle on a trailer is required (1) to meet the S5.3.2 stopping distance requirement with no uncontrolled lockup of any wheel above 10 mi/h, and (2) to meet the parking brake requirements for trailer converter dollies or for all other vehicles.

The answer to your first question is yes. The steerable axle(s) of any trailer must meet the stopping distance requirements of S5.3.2 with no uncontrolled lockup of wheels above 10 mi/h.

In answer to your second question, the permanently attached steerable axle you describe is not a separate vehicle which would qualify as a trailer converter dolly. Therefore the axle is simply part of a trailer which must meet the parking brake requirements of either S5.6.1 or S5.6.2. Neither of these options specifies that there be parking brakes on steerable axles, although in satisfaction of S5.6.2 (grade holding), the manufacturer could utilize parking brakes on the steerable axle.

Yours truly,

ATTACH.

April 12, 1974

James B. Gregory -- Administrator, National Highway Traffic Safety Administration

Dear Sir:

We manufacture a complete line of semi-trailers. Among these is a doubles grain trailer setup. In this doubles grain setup the lead trailer is a 24 foot, single axle semi-trailer which connects to the truck-tractor by means of a standard kingpin. The second trailer is a two axle, four wheel type of trailer, 21 foot long, which is connected to the lead trailer by means of a pintle hook-lunette eye attachment. The front axle on the second trailer is part of a dolly, which is steerable, and is permanently attached to the trailer by means of a bolted 360 degrees turntable.

Our question is one of interpretation. Is the front axle dolly a "converter dolly" in the sense that it would be exempt from having "antilock" and spring brakes as outlined in S5.8 of standard 121? Or is it to be classed so that it will require anti-lock and spring brakes? Your expeditious answer as to interpretation is appreciated.

Sincerely, Al Zajic -- Project Engineer, AMERICAN TRAILERS, INC.

Encl:

(Graphics omitted)

LEAD TRAILER

SECOND TRAILER

PERMANENT 360 DEGREES TURNTABLE