Weigh-in-Motion (WIM) systems are designed for weighing vehicles driving across a measurement site. Because during measurements the vehicle has to come in physical contact with the components of the system, WIM systems always use built-in sensors installed in road pavement. Each WIM system consists of force sensors placed in one, two or even several lines, perpendicular to the direction of traffic. The idea behind WIM systems is to measure the dynamic loads that the wheels of a moving vehicle exert on the road surface and, on this basis, to estimate static wheel loads as well as gross vehicle weight.