A semitrailer is a trailer without a front axle. A large proportion of its weight is supported by a tractor unit, a detachable front axle assembly known as a dolly, or the tail of another trailer.
A semitrailer is normally equipped with landing gear (legs which can be lowered) to support it when it is uncoupled.
Semitrailers are more popular for transport than full trailers, which have both front and rear axles. Ease of backing is cited as one of the semi's chief advantages. More
