Weigh-in motion (WIM) sensors measure the instantaneous axle weights of vehicles travelling at normal road speeds. The static axle or gross weights of the vehicles can be estimated by averaging the sensor outputs. The widespread use of WIM devices has been restricted by the unsatisfactory accuracy and poor reliability of the existing two-sensor systems. By using multiple WIM sensors, and thereby averaging more instantaneous axle weights, it should be possible to improve the accuracy of WIM systems. An array of eight axle sensors was installed in the A34 at Abingdon and assessed over a period of 7 months. The system proved reliable and over 93 per cent of the vehicles were weighed to within 10 per cent of their 'true' static gross weights. (A)

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