According to the Lewiston Morning Tribune, the weigh-in-motion system, or WIM, is located at the Lewiston Port of Entry on Highway 95, and consists of computers that assess sizes, weights and shipping credentials of trucks before they reach weigh stations. Trucks are allowed to bypass the static scale and can avoid stopping if they comply with state requirements.
Transponders in trucks are programmed by their companies to store data, including vehicles’ sizes, weights and shipping credentials.
Before reaching port of entry weigh stations, trucks pass under antennae suspended above the highway and drive across devices embedded in the road that detect the number of axles, distance between them and weight per axle. Computers set up at port of entry stations compare each truck's information with the measurements read by the in-road sensors. If the data matches measured parameters and if the semi is within transportation department requirements, a green light on the transponder signals the driver to keep on trucking.
Trucks can save up to 45 minutes each time it passes a weigh station with the new system. Port of entry officials say the WIM system also will allow the transportation department to concentrate enforcement efforts on size and weight violators.