Weigh in motion (WIM) technology may provide an efficient and cost-effective complement to static weighing. An evaluation of the effectiveness of an automated bypass system around a weigh station in Illinois is presented. The system combines the use of automatic vehicle identification (AVI), high-speed weigh in motion (HSWIM), and low-speed weigh in motion (LSWIM) technologies to facilitate preclearance for trucks at the weigh station. The preinstallation conditions were compared with postinstallation conditions of WIM/AVI so that the effects and benefits of the system could be evaluated. During preinstallation, average delay was 4.9 min/truck, and 7% of trucks had delays of more than 10 min. The station was intermittently closed to prevent the truck queue from backing up onto the Interstate highway, allowing 15 to 51% of trucks to bypass the station without being weighed. In postinstallation, the delay for trucks equipped with transponder and allowed to bypass on the freeway was reduced by 4.17 min. The delay for trucks equipped with transponders and allowed to bypass inside the weigh station was reduced by 2.02 min. The delay for trucks that reported to the weigh station decreased by 1.25 min. On the other hand, less than 1% of trucks that have been observed in after-study were able to bypass on the freeway. With greater numbers of trucks being checked, fewer trucks on the road may exceed the allowable weight limits. Consequently, electronic screening minimizes road deterioration and risks to public safety and levels the playing field for illegally operating carriers and carriers who operate in compliance with the law.