Gross vehicle and axle weight monitoring is useful in an array of applications including:
Weigh in Motion also applies to the railroad industry. Trains are weighed, either coupled in motion or uncoupled in motion. Coupled in motion weighing refers to a train weighing while all of the railcars are coupled. Uncoupled in weighing requires that the railcar be uncoupled on both ends in order to weigh. Uncoupled in motion weighing is generally reserved for railroad classification yards.
Recent years have seen the rise of several "specialty" Weigh in Motion systems. The most popular of these is the front fork garbage truck scale. In this application, a container is weighed -- while it is full -- as the driver lifts, and again -- while it is empty -- as the container is returned to the ground. The difference between the full and empty weights is equal to the weight of the contents.
In addition to trucks and railcars, airplane weighing is in use in some airports, whereby the plane taxis acros the scale bed, and its weight is measured. The weight may then be used to correlate with the pilot's log entry, to ensure there is just enough fuel, with a little margin for safety. This has been used for some time to conserve jet fuel.
Also, the main difference in these platforms, which are basically a "transmission of weight" application, there are checkweighers, also known as as dynamic scales or in motion scales. There is more information at Checkweigher.