During recent decades, increased use world-wide of weigh-in-motion (WIM) systems has brought new difficulties, which must be addressed to achieve accurate results. For example, potential customers need precision of the order of 1% at high speeds. Some frustrated users consider their results to be absolutely unusable. Two approaches are used for weighing a vehicle during its journey reasonably accurately: (1) avoidance of vertical vehicle oscillations, which requires either a perfectly even road surface, a built-in scales sensor precisely flush with the surface, and perfectly balanced wheels, or a drastic reduction of vehicle speed; and (2) measurement of the vehicle over a longer stretch, so that an average value can be determined. At present, the second method can only be used for research purposes, because it requires a sensor about 30m long. Achievable results with today's WIM technology range from about 1% to about 15%. In principle, good results can be obtained only with the best possible road quality and for vehicles with good suspension systems. A WIM system must satisfy different requirements, according to what information its users need. Suitable WIM systems are available for all current applications, but, in most countries, the police are still legally required to use static scales for weight inspection.
Abstract