The Transport and Road Research Laboratory supplies the Department of Transport with axle weight data, obtained using weighscales that are capable of measuring vehicles travelling at normal speeds. These data are used to establish trends in traffic loading and may be used for pavement and bridge design and evaluation. Trials have been carried out by the Laboratory to determine the overall accuracy of some of the twelve UK weighing sites, as well as an installation on the TRRL test track. Comparisons between the dynamic axle weights of moving Heavy Goods Vehicles (HGVs), as measured by the equipment, and their true static axle weights have been made. This was achieved by running four classes of HGV over six sets of weighscales at several speeds and at various levels of axle loading. This Report provides summaries of the trial data and a brief description of the weighscale equipment, its method of calibration, and the trial techniques used. Overall, an Impact Factor of unity (0.998) was achieved. However, the overall Coefficient of Variation of 15.3 per cent and the variation of mean IF between sites (from 0.89 to 1.08) shows that there is a requirement for sites to be individually calibrated. Dynamic axle Wear Factors show variations from the static axle wear factors ranging from -15 per cent to +54 per cent. (A)

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