WIM system calibration using AVI-equipped vehicles

This paper describes a method for calibrating weigh-in-motion (WIM) systems by comparing static and dynamic weights of vehicles through automatic vehicle identification (AVI). The AVI facilities developed for the heavy vehicle electronic license plate (HELP) project on the I-5 corridor was used for this purpose. The static axle load of AVI-equipped vehicles was obtained from the Oregon DOT for two sites, namely Woodburn South-bound and Ashland Northbound. The WIM load data was obtained from Lockheed IMS for all the WIM systems on the I-5 corridor. The data was analyzed to sort-out AVI numbers, dates and times of weighing. Time limits for traveling between sites were established to ensure that trucks had no time to stop and load/unload cargo between sites. Errors were calculated as the percent difference between WIM and static loads for individual axles/axle groups. Calibration factors were derived to set the mean axle weigh error to zero. Software was written to handle all calculations