Bridge-Weigh-In-Motion uses bridges as a scale to weigh vehicles. Practically, this is done by measuring the strains in that bridge, and relating them to the weight and dimensions of a truck called “calibration trucks” whose shape and axle weights are well known. This article summarizes different B-WIM experiments the institute IFSTTAR (formerly called LCPC) realized and the lessons drawn from this experience. First, the system has been tested on frame-type bridges with integral slab decks. Different parameters have been investigated like the quality of the surface of the pavement and the transversal shape of the road. Since, orthotropic plate bridges have been instrumented. Several points need to be further improved. B-WIM, Free of Axle Detectors