At present the use of weigh-in-motion systems to monitor truck axle loads and subsequently to control overloads is a very complex and costly procedure. Top Trial is a European research project having the following objectives: - set-up and use of a test site for developing and testing technologies of high-accuracy multi-sensor WIM systems (axle load weighing sensor arrays); - development of European standards for a future automated dynamic overload control; - development of proposals for a European user forum to increase road traffic safety, to protect the infrastructure and to guarantee a fair competition on the freight transport market on motorways. PTV coordinated the research project and had the overall charge of the test site set-up and the execution of the WIM trials. Top Trial used new methods and technologies for automatic overload control: the weighing station "A9 Baarer Weiher" near Ingolstadt combines two different technologies to weigh axle loads – bending plates and crystal sensors – in an optimised multi-sensor array. Weighing sensors monitor the loads in motion. A video camera records overloaded trucks and sends the pictures to the sorting point and the trial container. On a terminal at the sorting point the trucks and their percentage of overload are depicted on a video and then they are guided by the police to a near-by parking lot to be controlled. Here, the trial container with the necessary trial equipment and the calibrated reference scale, which determines the exact axle overload in slow motion, have been set up. Based on the trial results a high-accuracy WIM system to determine total weights and axle loads as well as to enforce overload automatically is to be suggested and the corresponding European standards have to be developed.