Transit Safety Retrofit Package (TRP): Leveraging DSRC for Transit Safety – Fielding Results and Lessons Learned
The Transit Safety Retrofit Package (TRP) project aimed to design and develop safety applications for transit buses that can communicate using vehicle-to-vehicle as well as vehicle-to-infrastructure connected vehicle technologies for enhanced transit bus and pedestrian safety. The project was part of the USDOT's Connected Vehicle Safety Pilot Model Deployment, a large-scale field demonstration of the potential benefits of 5.9 GHz dedicated short-range communications (DSRC) wireless technology that is supporting related decisions by the National Highway Traffic Safety Administration.
The specific objectives of the TRP project were to design and develop safety applications for transit buses that can communicate using Vehicle-to-Vehicle (V2V) as well as Vehicle-to-Infrastructure (V2I) Connected Vehicle technologies for enhanced transit bus and pedestrian safety. Program managers wished to determine if DSRC technologies could be combined with on-board safety applications to provide bus drivers real-time alerting of potential and imminent crashes. During the project, the USDOT deployed five collision avoidance applications on University of Michigan transit buses, including two new applications that address high-priority concerns identified by transit agencies- pedestrian crosswalks and vehicles turning in front of transit buses at bus stops. The source report focuses on the technical performance, effectiveness, and efficiency of the communication systems and driver vehicle interface (DVI) and contains related findings and lessons learned.
To achieve the objectives of the study, the TRP project included developing, testing, installing, and maintaining retrofit packages on three transit buses drawn from the University of Michigan transit fleets, including installation of three Basic Safety Applications and development of two new transit safety applications – Pedestrian in Signalized Crosswalk Warning (PCW) and Vehicle Turning Right in Front of Bus Warning (VTRW). Data were collected from the equipped buses for independent evaluation. The new transit safety applications are described in more detail below:
PCW: This V2I application warns a bus driver if pedestrians are in the intended path of the bus when making a right or left turn. This application incorporates two methods of detecting pedestrians—activation of the crosswalk button by a pedestrian and a microwave motion sensor that detects the presence of pedestrians in the crosswalk. The application provides two levels of alerts to the driver—an informational/cautionary indicator if the crosswalk button is activated and an imminent warning if a pedestrian is actually detected in the crosswalk. The PCW application was deployed at the intersection of Fuller Road and Medical Center Drive, in Ann Arbor, MI, next to the University Medical Center. This intersection was chosen because it was an RSE / SPAT-enabled signalized intersection on a well-used bus route with significant pedestrian traffic.
VTRW: This V2V application warns a bus driver of the presence of vehicles attempting to go around the bus to make a right turn as the bus departs from a bus stop. The application includes two levels of alerts to the driver—an informational/cautionary indicator if an equipped vehicle has moved from behind to beside the bus and an imminent warning if the equipped vehicle shows intent to turn in front of the bus. The VTRW application was deployed at 17 bus stop locations on the University of Michigan Commuter North and Commuter South routes. These routes were chosen as best suiting the purpose of this application – detecting other vehicles traveling in the same lane as the bus, then forced to change lanes in order to pass the bus when it is stopped at a bus stop.
More information on the benefits impacts on transportation system will be available in a separate report -- expected in 2015 -- in Transit Safety Retrofit Package Development Final Report, FHWA-JPO-14-142.
The TRP system was originally deployed onto the three University of Michigan transit vehicles with a full complement of TRP hardware and software on February 1, 2013. The system was used typically 12 hours per day for an eight-month deployment period. The development team collected and analyzed data from the deployment, developed limited system refinements based on initial lessons learned, and redeployed the refined system for four weeks during February and March 2014. The development team analyzed the PCW and VTRW event data as compared to ground truth (objective data recorded by the video-based Data Acquisition System (DAS), to assess the performance of the applications and determine lessons learned.
The TRP on-bus software was effective at providing alerts to transit drivers.
- The transit drivers expressed acceptance of the TRP concept.
- There was a high rate of false alerts for the PCW application due primarily to a combination of GPS limitations and pedestrian detector limitations.
- There was a high rate of false alerts for the VTRW application due to GPS limitations.
- DSRC radio technology performed well – there were no TRP problems traced to DSRC radio communications.
- The short-term system refinements yielded expected performance improvements.