Doubles/Triples · Coupling and Uncoupling
What is the correct order for coupling a triple-trailer rig?
Explanation
A triple is built front to back: couple the tractor to the first trailer exactly as for any tractor-semitrailer, then wheel a converter dolly into place behind it and couple the first trailer to the second the same way doubles are coupled, repeating the step to add the third. Uncoupling runs in reverse, pulling the rearmost dolly out first and then breaking the rig down as an ordinary double. 49 CFR 383.115(a) names procedures for assembly and hookup of the units as required knowledge for this endorsement without specifying the order, so the sequence is attributed to the manual. The wrong options all call for moving trailers that have nothing to move them: assembling the set on the ground or starting from the rearmost trailer means coupling units with no tractor attached to position them, and a converter dolly couples one trailer to the one ahead of it rather than two trailers to each other.
Source: 49 CFR 383.115(a)
Related Coupling and Uncoupling questions
- Under 49 CFR 393.70(c), a full trailer must be equipped with a tow-bar and a means of attaching it. What does that paragraph require of the tow-bar and its attachment?
- A converter dolly is coupled to a trailer by a tow-bar, and the required safety device has to be attached to the towing vehicle. Under 49 CFR 393.70(d)(1), where may it not be attached?
- 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?
- You are coupling a set of doubles, and the second trailer has no spring brakes of its own. How should it be secured before you couple it?