By: Eric Hemphill, P.E.
Wrong-way driving is an evergreen issue for transportation providers worldwide.
Resulting crashes, while a small percentage of overall accident statistics, tend to be severe—head-on and at high speed.
In the Dallas/Fort Worth region, the North Texas Tollway Authority (NTTA) has been intensely focused on studying and preventing catastrophic wrong-way crashes for more than a decade. In 2009, NTTA formed a task force to create and deploy methods to reduce wrong-way driving and crashes. The task force immediately identified simple, low-cost measures, including modifying pavement markings at several crossroad service streets to clarify correct locations for turns; installing red reflective tape on “Wrong Way” sign posts facing the potential wrong-way driver; installing reflective pavement markings that form an arrow on exit ramps to indicate the correct flow of traffic; and “Wrong Way” signs with solar-powered flashing LED lights at locations with low ambient light.
As the work of the task force continued, NTTA developed a wrong-way driver detection system using sensors embedded in the pavement at tolling points. The system is monitored by teams in the Safety Operations Center (SOC), a 24/7 traffic management and state trooper-dispatch facility. When a wrong-way driver crosses the sensors, it triggers an alert in the SOC. Staff then contacts troopers and local police and activates overhead signs to warn other drivers of the wrong-way driver.
Unfortunately, most wrong-way drivers are impaired by alcohol or drugs. Sober drivers usually scan the road in front of them as they drive, but studies completed by the Texas A&M Transportation Institute show that intoxicated drivers tend to focus their eyes on the pavement directly in front of them. In response, NTTA installed lower-than-standard “Wrong Way” and “Do Not Enter” signs as a way to catch the attention of impaired drivers. Compared to a sign mounted at 3 ft, the 2-ft installation height increased the signs’ retroreflectivity by 78%. In locations where they were installed, the lower signs reduced the number of wrong-way drivers by approximately 50%.
The task force expanded its aim to prevent and correct wrong-way driving beyond NTTA roads, including local streets. The team found that cities were willing to pitch in to help, allowing NTTA to modify pavement markings on their streets, install additional signage, and even close openings in medians to reduce driver confusion.
As technology changes, so does NTTA’s approach; in recent years, NTTA installed thermal cameras to assist in detection.
Prior to using thermal imaging cameras, NTTA experimented with detecting wrong-way drivers using standard roadway cameras. However, the glare from headlights at night caused false alarms, making the system unreliable. Thermal cameras only see heat signatures, which eliminates issues with headlight glare. A thermal camera detects abnormal heat signatures caused by a vehicle headed in the opposite direction of traffic and sends an alert to the SOC. NTTA has installed 20 of these cameras along its roads to supplement pavement sensor detection.
NTTA’s work continues toward deterring wrong-way drivers from entering its roads from the start (headed the wrong way up exit ramps). However, recent research shows that approximately one-third of wrong-way drivers entered the road headed in the correct direction before making a U-turn to drive into oncoming traffic. As a result, focus shifted to the drivers who did not initially enter the roadway incorrectly.
In 2019, NTTA installed a set of flashing signs connected to its pavement sensors. If a wrong-way driver crosses the sensors, automated systems alert the SOC and program unique digital signs near the sensors to flash a “wrong way” message. The signs stop flashing after one minute and are blank the remainder of the time. Traffic going the correct direction sees only the back of the sign with no message. Tests of these signs linked to sensors were successful; the system will be expanded to other locations over the next few years.
NTTA is now preparing to test the use of connected-vehicle technology to help identify cars driving toward oncoming traffic. The technology will pinpoint the wrong-way driver and send an alert to other vehicles in the area. The recent pandemic has slowed the progress of this project, but NTTA is continuing to prepare the test sites. Preventing wrong-way drivers from causing a crash is vital, and NTTA’s preventative measures and innovation have helped keep drivers safer.
About The Author: Hemphill is Director of System & Incident Management, North Texas Tollway Authority.
