The European WIM specification, prepared by the COST323 management committee, gives an indication of what WIM system accuracy might be achievable from sites with particular characteristics, and what accuracy might be acceptable for various needs. Calibration and testing procedure for WIM systems are considered. Accuracy classes are defined on the basis of the width of the confidence interval within which the measured results lie. For each class, confidence interval widths are specified for gross weights, weights of axles, etc., and the required level of confidence is fixed with respect to the test conditions and the number of test runs. A simplified requirement with standard test plans is proposed for common acceptance tests. For the covering abstract see IRRD E102667.