VEHICLE CONFIGURATION INFLUENCES ON WEIGH-IN-MOTION RESPONSE

Statistics on axle and vehicle masses traditionally have been collected by stopping and weighing vehicles on axle or whole-vehicle weighers. This technique is still applicable but only on roads carrying low truck volumes or in instances in which only a small sample of the population is required. On heavily trafficked roads this technique is extremely hazardous. Because of the inherent limitations of static weighing, considerable developments have taken place in the last decade on systems that permit the collection of data on axle and vehicle masses. These data are recorded while the vehicles travel at normal highway speeds without interference to the traffic stream. These systems are commonly known as weigh-in-motion (WIM) systems. The dynamic pavement loading, by simulation, of various vehicle configurations on a range of pavement roughnesses where WIM installations could be made are reported. In the evaluations the mass variations are attributed to the dynamic influences, although the precision of the measuring system is not taken into account. The simulation procedure is presented and its use is justified by comparing simulated results with measured axle masses. Variation in all the axle loads of various vehicles along sites that typically could be appropriate for WIM, ideally having a pavement serviceability index greater than 3.0, are presented. The influence of the systems flush with the surface and placed on the surface are considered. The effectiveness of WIM to measure vehicle masses is then presented. Finally the implications of these results of WIM accuracy, calibration, and weighing are discussed.