What is a Big Rig?
The term big rig is a colloquialism for a semi-truck or a tractor-trailer. A big rig is a two-part truck that consists of both a tractor and a trailer. The driver sits in the tractor or cab and a trailer is hooked to the tractor. Freight is transported in the trailer portion. In the United States, big rig tractors normally have three axles: the front or steer axle and two rear or drive axles. The steer axle of a big rig usually has two wheels, while each drive axle has a pair of double wheels on each side of the axle. This translates into 10 wheels for the most common type of big rig tractor.
