The Doubles and Triples endorsement test

More than one trailer

The endorsement covers pulling two or three trailers behind one tractor, and the test exists because a second trailer changes the way the whole thing behaves rather than simply making it longer.

Five subjects

49 CFR 383.115 sets them. Assembly and hookup of the units. Proper placement of the heaviest trailer. Handling and stability characteristics. Problems in traffic operations. Operating practices and procedures.

The second one is a rule, not a preference

Proper placement of the heaviest trailer gets its own line in the federal list, which tells you the test asks about it directly. Heavy goes in front, light goes behind, and the reason is stability rather than convenience. A candidate who knows only the rule and not the reason will answer the plain question and miss the one that describes a load and asks what to do with it.

Crack the whip

Handling and stability is where the rearmost trailer amplifies whatever the tractor does. A small correction at the front becomes a large swing at the back, and the swing gets worse the further back you go. Most of what makes this combination dangerous in wind, on curves and during lane changes comes out of that one effect.

Traffic operations

A separate subject from handling, and it is about the space the vehicle needs from everybody else: gaps that are long enough to enter, lane changes that take longer than a driver expects, and the fact that other traffic consistently underestimates how much road you are using.

Passing it

Three choices a question and 80% to pass. Our forms run twenty questions, which is our own length rather than New York's.