To Reduce Excessive Nuisance Alerts Generated by Transit Vehicle Collision Avoidance Warning Systems, Use Location Based Sensitivity Adjustments for Routes That Traverse Both Pedestrian Heavy Areas and Areas with Less Pedestrian Activity.
The Virginia DOT Evaluated Transit Vehicle Collision Avoidance Warning Systems (CAWS).
Made Public Date

Evaluation of a Transit Bus Collision Avoidance Warning System in Virginia


Even though bus operators are trained extensively, they can become distracted at times or fail to detect a vulnerable road user. In 2017, the Virginia Department of Rail and Public Transportation (DRPT) initiated a demonstration project to plan, implement, and evaluate a transit bus collision avoidance warning system (CAWS) on up to 50 buses. CAWS system included advanced driver assistance system that utilizes kinematic sensors and multiple external camera sensors to provide visual and/or audio alerts in various categories such as daytime pedestrian and bicyclist detection, warning for exceeding the speed limit, lane departure warning, and headway monitoring and forward collision warning (FCW). The goal of this study was to evaluate the CAWS deployment at multiple transit agencies in Virginia in terms of system effectiveness and bus operator acceptance. The system was installed on 51 buses at nine transit agencies. The analyses focused on bus operator feedback sessions, surveys, and quantitative differences in event rates on bus routes.

Lessons Learned

  •  Remember that CAWS can be overly sensitive. Based on the survey results, 75 percent of bus operators reported that the CAWS set off many false alarms about pedestrians and bicyclists when there were no pedestrians or cyclists present. Data collected while using CAWS should therefore be interpreted with caution.
  • Support transit agencies’ interests in deploying bus CAWS through offering matching funds, training, and expertise. The mixed results of this study suggested that the decision of whether to deploy CAWS should be left to each transit agency, but agencies choosing to do so may benefit from support. This could include providing matching funds, offering training, coordinating information exchanges, and/or making ongoing technical assistance available to ensure the system continues to function properly and the telematics data are accessible to the agency.
  • Continue monitoring the performance of CAWS. Further analysis is needed to learn about these systems as more data are collected and more bus operators use them. In the coming years, data should be further analyzed to determine if CAWSs are increasing performance and safety or are ultimately distracting drivers with a high frequency of false alarms.
Goal Areas