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Combination Vehicles · Coupling and Uncoupling

Under 49 CFR 393.70(d), what is required, in addition to the tow-bar itself, when towing a full trailer or converter dolly?

1.Either two safety chains or cables, or a single bridle chain or cable attached at two points, with strength at least the towed vehicle's gross weightCorrect answer
2.A single chain or cable attached at only one single point is enough, since the tow-bar itself already carries almost the entire actual load entirely by itself
3.No additional safety device of any kind at all is required if the drawbar already has its own built-in locking pin properly fitted
4.A second, fully redundant backup drawbar mounted directly beside the primary towing drawbar itself for some extra safety margin

Explanation

49 CFR 393.70(d) requires a full trailer or converter dolly coupled by a tow-bar to also be secured by a safety device: either two safety chains or cables, or a bridle arrangement of a single chain or cable attached to the towed vehicle's frame or axle at two points as far apart as the configuration permits, with combined strength at least equal to the gross weight of the towed vehicle. This is a distinct sub-item of the same coupling-devices section used for the fifth-wheel locking mechanism at 393.70(b)(2), not a separate regulation, and the duty is the regulation's alone; the WA guide is used here only as the topic map for tow-bar coupling, not as the source of the legal requirement. A single chain or cable attached at only one point is not sufficient; even that configuration must be arranged as a bridle attached at two separate points. A self-sufficient locking pin and a duplicate drawbar are invented alternatives that don't satisfy this specific safety-device requirement.

Source: 49 CFR 393.70(d)

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