Three times a day. That’s how often public safety officers in Arizona get an alert about someone driving the wrong way—about as frequently as most of us tie our shoes or wash our hands or sit down to eat a meal.

Between 2004 and 2014, that added up to nearly 9,000 wrong-way drivers on Arizona’s streets, highways, and freeways, leading to 245 crashes and 91 fatalities.  By August 2019, the state had seen as many wrong-way driving incidents as it had in the entire preceding year.

Faced with a serious and worsening public safety threat, the Arizona Department of Transportation (ADOT) has taken extensive steps to counter wrong-way driving. These have included adding signage, increasing penalties, launching an awareness campaign, and installing a first-of-its-kind detection and warning system along a stretch of freeway in Central Phoenix.

Stepping up signage

For decades, Arizona has used red-and-white “WRONG WAY” and “DO NOT ENTER” signs on its freeway ramps to notify drivers entering in the wrong direction. But in 2014, inspired by a report from the National Transportation Safety Board (NTSB) as well as initiatives in states like Florida and Texas, ADOT began to make some upgrades. These included:

  • Installing new, oversized wrong-way signage
  • Lowering the wrong-way signage height from 7 feet to 3 feet (studies have shown that alcohol-impaired drivers tend not to set their gaze lower than non-impaired drivers)
  • Installing red retroreflective stripping on signposts
  • Adding white pavement arrows pointing in the correct direction of travel

While ADOT believes that additional, enlarged, and lowered signage has helped get the attention of wrong-way drivers, they also knew signage alone wouldn’t be enough to get them to turn around.

Testing new technologies

ADOT began researching detection technologies for wrong-way driving in the early 2000s. These included microwave, Doppler radar, video imaging, thermal sensors, and magnetic sensors. The author of one study concluded that “wrong-way vehicles can be detected using easily deployable equipment that is currently available in the market.”

In 2015, ADOT piloted three systems that used radar to detect incoming wrong-way drivers and immediately trigger a “WRONG WAY” sign with flashing bright red LEDs. This gives drivers “a visible, real-time indication prior to highway entry.”

They expanded on this system in January 2018, installing a pioneering new detection and warning system at 30 exit ramps along the Interstate-17 in Phoenix. Beyond triggering a large, eye-level LED sign, the system also uses cameras to confirm the presence of a wrong-way driver, and sends an alert to the local traffic management center (TMC). Staff there can then broadcast warnings to other drivers on variable messaging signs and deploy authorities to the scene.

As of November 2019, the new system has detected more than 90 wrong-way driving incidents, nearly all of whom turned around on off-ramps before entering the freeway’s mainline lanes. ADOT is continuing to evaluate the detection and warning system, but already has plans to expand the technology to other high-conflict areas.

Learn more

> Wrong-Way Driving: Facts and Effective Countermeasures

> What states can learn from Florida’s wrong-way driving research

> New detection and alert systems in Nevada show promise