Weigh-In-Motion (WIM)

Weigh-in-Motion (WIM) systems are an array of sensors used to measure various features of vehicles in motion. WIM systems are comprised of not only the electronics and sensors but include just as importantly flat, smooth, and straight roadways. Data collected from WIM systems include: time and date, speed, vehicle axle counts, axle spacing, axle weight, gross vehicle weight, weight violations, vehicle classification, and overall length. The Caltrans WIM program started in 1987, with the first data site on Interstate 5 near Lodi. The WIM systems measure commercial truck weight while the vehicle is moving at either highway speeds or slow speeds. The mainline data WIM systems are only used for data collection, and are not used directly for inspection or enforcement. Bypass WIM systems are installed upstream of larger commercial vehicle enforcement facilities (CVEFs) by the California Highway Patrol. These systems are used in conjunction with a screening system used to check Department of Motor Vehicles and safety records of enrolled vehicles. In-station WIM systems are used to pre-screen trucks as they exit the mainline ramp at CVEFs to assist the processing of commercial trucks. For assistance, send email to Traffic Operations.