Semi-trailer truck

Summary

A semi-trailer truck is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer attaches to the tractor with a type of hitch called a fifth wheel. Semi-trailer trucks replaced traction engines in commercial and heavy haulage roles. This transition occurred primarily between the 1920s and 1950s, driven by the need for greater efficiency, speed, and reliability.