Automatic Vehicle Location and Computer-Aided Dispatch Systems: Design and Application Considerations

Automatic Vehicle Location (AVL) systems can track transit vehicles in real time. Computer-Aided Dispatch (CAD) software is used to monitor transit operations and assist management of transit operations. Together with AVL systems, CAD software can be used to replace a disabled vehicle by dispatching another vehicle, or meet fluctuating travel demand by adjusting transit headways, schedules, and routes. AVL and CAD technologies can vitalize transit by directly improving on-time performance, increasing transit efficiency through providing dispatchers with location, direction and status information, and reducing operating costs through reducing dependence on transit field supervisory personnel. Direct benefits to travelers can include higher reliability of travel times and reduced stress in dealing with transit unreliability. This study explores the development, availability, and impacts of AVL/CAD technologies as reported by AVL vendors and transit implementers. The study defines the key features, functions, and performance characteristics of AVL/CAD technologies that can influence the level of benefits realized. The AVL/CAD implementation context is explored by examining where, when, and for what users these systems are being implemented. The results of two surveys are reported. To explore the availability of AVL/CAD systems, technology suppliers were surveyed. Suppliers identified the features, functions, and performance of available AVL/CAD technologies. To determine the extent of AVL/CAD deployment, transit operators were surveyed regarding their experiences with AVL/CAD technologies and the subsequent impacts on travelers and transit agency performance. This research provides a systematic method for evaluation of AVL/CAD systems and reports the perceptions of AVL/CAD vendors and transit implementers regarding available products and their impacts. The results suggest a need for better tools to characterize and quantify the impacts and benefits of AVL/CAD systems