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是牽引車、第一半掛車及連接在其後部第五輪上的第二半掛車的組合。不能把這個20米結論籠統套給所有拖掛結構；某些其他組合及特定窄載物後伸情況有不同長度規則。