Following completion of Federal Highway Administration (FHWA)-sponsored research in high-speed weighing of vehicles using instrumented bridges as the load-sensing element, the South Dakota Department of Transportation became interested in the technology as an appropriate means for gathering truck weight information. After unsuccessful efforts to obtain a prototype system from the FHWA, the Department decided in late 1982 to develop its own bridge weigh-in-motion system. Electronic equipment was purchased, weighing software was designed and written, and a motorhome was purchased to house and transport the system. Two bridges were permanently instrumented and used for weighing in 1983. Although it was based on research published during the FHWA-sponsored contracts, the system has been developed independently and differs from the prototype systems. Permanently bonded strain gauges are used instead of removable transducers, and photocells are used rather than tapeswitches to sense axles. Calibration procedures are also different. As of fall 1985, eighteen bridge weigh-in-motion sites in South Dakota are being used to conduct the state's Truck Weight Study on interstate, main rural, secondary and urban highways.