DOT and Battelle release findings and lessons learned from V2X Transit Safety Retrofit Package project

13 December 2014

The US Department of Transportation (DOT) and Battelle have released the latest findings and lessons learned from the Transit Safety Retrofit Package (TRP). The 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 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.

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During the project, the USDOT and Battelle deployed three basic collision avoidance applications (Forward Collision Warning (FCW), Emergency Electronic Brake Lights (EEBL), and Curve Speed Warning (CSW)) on three University of Michigan transit buses. In addition, and two new applications addressed high-priority concerns identified by transit agencies: Pedestrian in Signalized Crosswalk Warning (PCW) and Vehicle Turning Right in Front of Bus Warning (VTRW).

• FCW: This V2V application warns a bus driver when there is a risk of a rear-end collision with an equipped vehicle in the same lane in front of the bus. FCW is intended to help drivers in avoiding or mitigating rear-end vehicle collisions in the forward path of travel.

• EEBL: This V2V application warns a bus driver when there is a hard-braking event ahead of the bus from an equipped vehicle in the lane ahead of the bus or in an adjacent lane. The vehicle initiating the hard-braking may be several vehicles in front of the bus. EEBL is particularly useful when the bus driver’s line of sight is obstructed by other vehicles or bad weather conditions (e.g., fog, heavy rain).

• CSW: This V2I application warns bus drivers when they are approaching or entering a curve at too high of a speed to negotiate it safely. CSW relies on roadside equipment and therefore is only available at designated locations.

• 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.

• 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.

In addition to the safety applications, elements involved in TSP project included:

• Transit Vehicle On-Board Equipment (OBE) – The DENSO miniWSU Wireless Safety Unit (WSU) included a DSRC radio that received and transmitted Basic Safety Messages (BSMs) via 5.9 GHz DSRC. The miniWSU interoperated with other Model Deployment vehicles and Roadside Equipment (RSE) according to Institute of Electrical and Electronics Engineers (IEEE) 802.11p and 1609.2 standards and the SAE International J2735 message standard.

• Crosswalk Motion Sensors – The MS SEDCO SmartWalk XP was used to detect pedestrians in intersection crosswalks in support of the PCW safety application. These units were mounted to existing poles at a recommended height of 10–12 feet, and employed microprocessor-analyzed Doppler microwave detection technology.

• Data Acquisition System (DAS) – The University of Michigan Transportation Research Institute (UMTRI) DAS was used to record data for the purpose of TRP evaluation, including data from the vehicle CAN bus, four video cameras, a range/position sensor, and the basic safety applications.

Illustration of the TRP system. Click to enlarge.

The system was used typically 12 hours per day for an eight-month deployment period.

The major conclusions and lessons learned from this project are:

• 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.

• Wide Area Augmentation (WAAS)-enabled GPS accuracy is insufficient for the PCW and VTRW applications. Typical lane width is 3.35 meters, thus accuracy within 1.675 meters is required, which cannot reliably be achieved with WAAS-enabled GPS. A more precise technology, such as Differential GPS, should be employed on future systems to achieve expected performance levels.

• The Doppler microwave-based crosswalk detectors are insufficient for the PCW application. A more discerning technology, such as high-speed imaging, should be employed on future systems to achieve expected performance levels.

• DSRC radio technology performed well—there were no TRP problems traced to DSRC radio communications.

• The short-term system refinements yielded expected performance improvements.