What is the standard maximum overall length of a B-train combination, including its load, when operating without an overlength permit?

A B-train consists of a towing vehicle, a first semi-trailer and a second semi-trailer attached to a fifth wheel at the rear of the first. Other combinations and specified narrow projecting loads can have different length rules.

B-train是牵引车、第一半挂车及连接在其后部第五轮上的第二半挂车的组合。不能把这个20米结论笼统套给所有拖挂结构；某些其他组合及特定窄载物后伸情况有不同长度规则。