Correlation exercise on TRRL weighscale installation

For many years, TRRL has operated a number of high speed axle weighscale installations at sites on the public road network to monitor and forecast average axle wear factors for use in pavement design. Before observations are taken, each installation is calibrated statically. The present exercise was undertaken to examine in more detail, the accuracy of the equipment. This involved a series of correlation tests using lorries of known static weight passing at normal traffic speed over the installations. A comparison between the weighscale reading and the known axle weight of the vehicles gave the correlation factors. The analysis shows that the weighscales are, on average, recording 5% heavy but this has varied between sites, from +15% to -9%. The analysis indicated that the factors were not significantly affected by the speed of the vehicles or the static weight of the individual axles. (A)