A full trailer towed by a tow-bar must have either two safety chains or cables, or a single chain or cable arranged as a bridle. Under 49 CFR 393.70(d)(6), what is different for a converter dolly with a solid tongue?

Explanation

49 CFR 393.70(d)(6)(i) permits safety chains or cables on such a dolly to consist of either two chains or cables or a single chain or cable used alone. The condition is narrower than the phrase solid tongue alone suggests: the paragraph reaches a converter dolly with a solid tongue and without a hinged tow-bar or other swivel between the fifth wheel mounting and the attachment point of the tongue eye or other hitch device, so a dolly that does have such a swivel is not covered by the allowance. It exists because a rigid, non-swivelling tongue already resists the sideways movement a bridle is there to control, and the same paragraph adds at (d)(6)(ii) that a single device must be in line with the centerline of the trailer tongue. For a full trailer, (d)(5) still requires two chains or cables, or a bridle arrangement of a single chain or cable attached to the frame or axle at two points as far apart as the configuration permits. The wrong options generalise or discard the allowance: it is not available on any dolly or full trailer whatever its tongue, a solid tongue does not remove the safety device requirement at all, and no three-chain configuration appears in the section.

Source: 49 CFR 393.70(d)(6)(i)