A warning system being tested along 15 miles of Interstate 17 in Phoenix alerted authorities to a vehicle traveling the wrong way.
No crash resulted from the incident early Thursday and the wrong-way driver was arrested on suspicion of DUI.
You can watch video of the detection as it happened in the player above.
Arizona Department of Transportation officials say it was the first vehicle detected on I-17 travel lanes in Phoenix since the wrong-way system went into operation in January.
Officials said in June that more than 15 vehicles have been detected entering I-17 off-ramps and frontage roads. None of those vehicles entered the I-17 mainline and most drivers turned around in the correct direction on the exit ramps, ADOT says.
“We’ve never been able to see what’s happening at these ramps,” said Steve Elliott, a spokesperson for ADOT. “Thermal cameras show that many of them self-correct.”
The $4 million system includes 90 thermal detection cameras positioned above exit ramps and the mainline of the freeway between the Interstate 10 "Stack" interchange near downtown Phoenix to the Loop 101 interchange in north Phoenix.
It's designed to alert authorities so traffic operators can warn other drivers via overhead message boards and state troopers can respond faster than relying on 911 calls.
“We will continue to improve the system to make sure that it’s as good as it can be,” Elliot said.
“We’re the first-state-in-the-nation system. Other states are seeing what we’re doing as they deal with their problem of wrong-way driving,”