Bridge weigh-in-motion deployment opportunities in Alabama
Overweight vehicle enforcement is a continuous problem for all state Departments of Transportation. Various technologies are in use across the US to aid in the enforcement of vehicle weight limits. However, to date, no technology has been shown to be a definitive solution. The various technologies currently available were researched and the pros and cons of each highlighted. Focus was placed on Bridge Weigh-in-Motion (B-WIM) and an extensive literature review has been conducted following all developments in the field of B-WIM since 1979. The advantages of B-WIM include its ease of installation, portability and potential for high accuracy vehicle weight measurements. Accuracy however is site specific, which makes the selection of a bridge an extremely important element in the success of a B-WIM installation. A bridge selection tool prototype was developed using ArcGIS. The tool was designed to select bridges with the physical characteristics associated with achieving high B-WIM weight measurement accuracies. Daily truck volumes and current Weigh-in-Motion (WIM) sites were also included in the tool to allow for an effective choice of route for installation. As the systems use cellular data signals to transfer data to the weigh crew during the pre-selection process, cell service maps were also included in the tool. The prototype showed that such a tool is feasible and should be beneficial for ALDOT. ALDOT owns two B-WIM systems which it intends to use for overweight vehicle enforcement. An accuracy test of the system was conducted. A bridge in West Alabama was selected for installation. Calibration was conducted and random vehicles were statically weighed to verify the accuracy of the system. A gross vehicle weight accuracy of B (10) was obtained which is more than sufficient for pre-selection of potentially overweight vehicles. Alternative sensor locations and orientations were also investigated and signals were compared. It was found that longitudinal axle detectors located close to the bridge supports provided the cleanest and most distinct signals at the test location. Weighing sensors located at the mid-span provided the best signals for weighing trucks.