This report examines three methods of monitoring overloading of goods vehicles: (i) using data from enforcement statistics; (ii) weigh-in-motion systems which measure the weight of each axle of vehicles travelling at normal highway speeds; and (iii) random surveys of goods vehicle weights. The potential sources of error in weighing vehicles are examined as are the effects of these errors on the apparent overloading rate. Other factors affecting the choice of method, such as knowledge of the maximum permitted weights, sample composition and time coverages are also examined. The report concludes that enforcement statistics indicate the efficiency of selecting vehicles to weigh rather than the rate of overloading, that random surveys can provide useful information on overloading but are expensive and cover limited time periods, and that the accuracy of weigh-in-motion systems needs to be substantially improved before they can serve as a useful method for monitoring overloading. (Author/publisher)
Abstract