Three Wrong-Way Driving Prevention Systems were Tested and Evaluated at Off-Ramps in Nashville, Tennessee.
Crashes due to wrong-way driving can occur when a vehicle enters an exit ramp in the opposite direction from the legal traffic flow and continues onto the highway. Researchers in Tennessee evaluated three commercially available Wrong-Way Driving Prevention Systems (WWPS), after conducting a literature and crash data review, and surveying vendors in December 2019. Typically, countermeasures triggered by WWPS include a flashing light-emitting diode (LED) equipped wrong-way sign which alerts the driver entering the wrong direction of traffic, followed by an “alert to authority” which sends a text message or email via accompanying software to the Traffic Management Center. Testing was first performed using each of three WWPS products on a closed environment without external traffic. Then, during the first half of 2021, the WWPS were installed for one month of field testing, using a different Nashville off-ramp for each system. The researchers evaluated the performance of each system based on five criteria:
- Accuracy – rate at which the WWPS correctly determines the type of event, with Missed Detection Rate performance weighted at twice the False Detection Rate performance
- Responsiveness – how quickly the WWPS reacts to a wrong-way driver event, including Flashing Sign Delay and Authority Alert Delay
- Live Tracking – how well the WWPS performs over an extended period of time
- Cost – equivalent annual cost based on life cycle cost analysis
- Other factors - ease of installation, software features and product deployment history (how long product has been available and extent of deployment across the country)
- Check the camera angle of the detection component and test different vehicle speeds for detection of Wrong-Way Drivers. A few missed detections were found during test speeds of 30 and 40 mph. This was mainly due to the camera angle of the detection component being too low and insensitive at higher speeds. Raising the mast arm and adjusting the speed sensitivity helped reduce such missed detections.
- Ensure the system’s two-zone setup (alert zone and confirmation zone) is tested to avoid unnecessary notifications. In one experiment, the test vehicle was instructed to cross the alert zone and stop, which triggered the first countermeasure for all three WWPS. After making a U-turn, the second countermeasure, the notification alert to authorities, was not triggered, indicating that the system’s two-zone setup worked as intended.
- Consider the number of flashing LED-enhanced wrong-way signs and speed of response to the Wrong-Way Driving event. The flashing LED-enhanced wrong-way sign requires a short response time to ensure it is activated and seen before the vehicle passes the sign.
- Evaluate the cost-effectiveness of the system using life cycle costs. Deployment cost, annual maintenance cost as well as the length of useful life of the system should be considered for overall cost evaluation. The expected useful life of a system can have a sizeable effect on the life cycle cost analysis.
- Investigate if the design of the current notification system meets the agency needs. For example, one system sends an email containing a 20-second evidence video that is good for validation. However, that can result in increased delivery time. Using a two-step alert notification, where an initial text alert is sent, followed shortly by a separate email with video, can reduce the initial latency.
- Consider the possibility of complex installation and calibration requirements when selecting a WWPS system. Some systems may require more steps than others in the initial setup. For example, one system required either a bucket truck or ladder to calibrate the radar and camera at the top of the pole.