Calibration of Weigh-In-Motion systems – metrological assessment of methods for determining reference values

The increasingly common practical application of systems for the dynamic weighing of vehicles in motion makes necessary periodic assessment of correct operation of such systems and calibration of the results obtained from them. This paper presents an experimental study and the obtained measurement results which allow for the determination of reference values essential for the calibration process. It was assumed that Weigh-In-Motion (WIM) systems will be calibrated using the pre-weighed vehicle method. The desired reference values in this case are thus gross weight (Gross VehicleWeight – GVW) and static load of individual test vehicle axles used in the calibration process. The experiments and analysis of results obtained from them presented in this work involve the use of a platform scale for determination of GVW, as well as portable scales or a dynamic low-speed scale (LS-WIM), intended for measurement of the loads of individual axles of vehicles. All of the scales used in the experiments have valid certificates of metrological approval. The results obtained indicate the possibility of significant simplification of the procedure while still maintaining the required accuracy. The simplification proposed involves the possibility of abandoning the GVW measurement on the platform scale, instead determining this value by summing up the load measurements of all the vehicle’s axles obtained on the LS-WIM scale.