Abstract: A method of assessing the accuracy of a roadside traffic monitoring system (TMS) arranged to measure the speed and/or other parameters of vehicles passing a predetermined measurement point adjacent the TMS is disclosed. The method includes measuring the speed of each vehicle passing the measurement point using the TMS, measuring the moment in time that each vehicle passes the measurement point using the TMS, and recording the measured speeds and times as data pairs. The method further includes driving an Instrumented Probe Vehicle (IPV) at the measurement point, the IPV having an onboard system for measuring speed, determining the location of the IPV, determining a calibration time at which the determined location of the IPV corresponds to the location of the measurement point, and measuring a calibration speed of the IPV using the onboard system when the determined location of the IPV corresponds to the location of the measurement point.

Abstract: A vehicle detector and classifier comprises a plurality of electrically conductive loops 1 arranged substantially in a plane perpendicular to a road surface, for detecting vehicle wheels. The loops can be arranged in a transverse, vertical slot 2 and housed in a flexible enclosure. An electronic circuit 3, including an oscillator, can be positioned adjacent each loop 1 in the slot 2 to energize and monitor the loop. The detector preferably also includes a conventional loop arranged substantially in the plane of the road surface, for detecting vehicle bodies, and means for superposing the results obtained from the conventional and vertical loops to aid in classifying detected vehicles.