Staying alive

Jan. 2, 2019

Thermal camera wrong-way driver alert system saves lives in Phoenix

At 1:11 a.m. following the 2018 Fourth of July celebration, a vehicle traveled southbound in the northbound lanes of north Phoenix’s I-17 at Union Hills Road.

Immediately, the wrong-way driver detection system installed earlier in the year set off a system alarm. A loud horn went off in the Arizona Department of Transportation (ADOT) traffic operations center, and pop-up windows appeared on operator workstations showing video from a thermal camera stationed near the exit ramp where the driver entered in the wrong direction.

Using a computerized decision support system, operators activated wrong-way warnings on freeway digital message boards to alert other drivers and urge them to exit the freeway out of harm’s way. Ramp meter signals turned on with a red-only light to deter drivers from entering the endangered lanes. Fortunately, shortly after the alert sounded, the wrong-way vehicle exited the freeway, turned around and re-entered I-17 going the right way in the northbound lanes. Traffic operators and the Department of Public Safety (DPS) continued tracking the vehicle, and state troopers stopped the vehicle and took the driver into custody on suspicion of driving under the influence.

The ADOT system operating that evening was part of a first-of-its-kind wrong-way driver detection pilot program being tested along a 15-mile-stretch of I-17 in Phoenix. According to ADOT, no crash resulted from the incident, the first vehicle detected on I-17 since the wrong-way system began operating in January 2018.

According to ADOT, the $4 million system includes 90 thermal detection cameras positioned above exit ramps and the mainline of the freeway between the I-10 “Stack” interchange near downtown to the Loop 101 interchange in north Phoenix. It is designed to provide immediate alerts to ADOT and DPS so traffic operators can quickly warn other drivers via overhead message boards, and state troopers can respond faster than relying on 911 calls from other drivers. If the detection is at an off-ramp, an internally illuminated wrong-way sign with red flashing LEDs will activate, positioned along the ramp to attract the attention of wrong-way drivers, most of whom are impaired, often severely.

The $4 million wrong-way detection system includes 90 thermal detection cameras positioned above exit ramps and the mainline of the freeway between the I-10 “Stack” interchange near downtown to the Loop 101 interchange in north Phoenix.

National picture and research

Nationally, attention has been raised on wrong-way driving and related fatalities, as each year 300 to 400 people are killed on the nation’s highways. Many states have conducted their own studies on wrong-way driving, confirming the findings unearthed by the National Transportation Safety Board’s (NTSB) 2012 comprehensive wrong-way driving study.

Key findings were that 60% or more of fatal wrong-way crashes were caused by drivers impaired by alcohol, and that drivers over the age of 70 are overrepresented as at-fault drivers in wrong-way collisions. The primary origin of wrong-way movements is entering an exit ramp, followed by making an S-turn on a divided highway using an emergency turnaround.

Most wrong-way collisions occur on weekends, especially between 6 p.m. and 6 a.m., and disproportionately after midnight. Because of the head-on or high-speed sideswipe nature of accidents, wrong-way accidents have a higher percentage of fatalities.

Full, four-quadrant cloverleaf ramps have the lowest wrong-way entry rate and left-hand exit ramps have the highest. Partial interchange, loop exit ramps and exit ramps that terminate at two-way streets have been associated with wrong-way driving.

The study also said most of the methods available to stop a wrong-way vehicle involve a high degree of risk and may put law enforcement officers and other motorists in jeopardy. For example, Utah patrol officers have used the technique of meeting wrong-way drivers head-on to stop them. They now try to isolate the wrong-way driver and use box-in tactics.

The NTSB found that providing navigation system alerts that inform drivers of wrong-way movements onto controlled-access highway exit ramps before they reach mainline traffic could enhance safety, and that for wrong-way navigation alert systems to be reliable and effective, global positioning system providers must follow consistent human factors policies in messaging and alerting.

Program origins

The ADOT Traffic Engineering Group provided data for analysis of all crashes that occurred from 2004 through 2013, published in November 2015 as “Detection and Warning Systems for Wrong-Way Driving” by the ADOT Research Center. The urban highway with the greatest rate of wrong-way crashes per mile was found to be a 39-mile segment of I-17 in metropolitan Phoenix.

By extrapolating data from crash maps, the ADOT study showed there were approximately a dozen wrong-way driving crashes with four fatalities in the 15-mile test area of I-17 during the study period of 2004 to 2013. The wrong-way problem has persisted since that study. In 2017, according to the DPS, there were a total of four wrong-way crashes, two of which were fatal, that resulted in four fatalities along the test area. For example, in April 2017, a wrong-way collision resulted in three fatalities. Two months later, another wrong-way accident caused a fatality. After another crash on the S.R. 51 ramp to I-10, the governor decreed that ADOT and the DPS take action. Relying on a significant amount of prior study and work on wrong-way driving prevention, ADOT accelerated design and deployment of the pilot program.

Success—so far

ADOT said the wrong-way driving detection system installed in 2018 has recorded more than 30 vehicles traveling on I-17 off-ramps and frontage roads in the wrong direction, but the drivers were able to turn around or self-correct on the exit ramps without entering the mainline freeway in the wrong direction. The internally illuminated flashing LED wrong-way sign may have alerted the wrong-way drivers to their error in some of the 30-plus incursions. Ultimately while the system cannot prevent wrong-way driving, it is designed to detect wrong-way driving more quickly than relying on 911 calls. It allows a faster response by law enforcement officers.

Since the test system became operational on Jan. 1, 2018, one wrong-way driver traveling the wrong direction in the northbound lanes of I-17 within the 15-mile wrong-way driving detection pilot project limits caused a three-car accident at 2:42 a.m. on Aug. 4, 2018. Only minor injuries were reported. The crash occurred less than 2 miles from where the wrong-way driver entered the freeway, therefore there was little chance for DPS to intervene in time. There have been no other wrong-way driving accidents in the test corridor during 2018.

Wrong-way driving accidents comprise a relatively small percentage of traffic accidents, but the outcomes are often tragic. Agencies need to continue to explore various technologies to address wrong-way driving issues. The ADOT test pilot using thermal imaging cameras, improved signage and internally illuminated wrong-way signs shows promise. Hopefully, future advancements in technology such as these will provide cost-effective tools to address the wrong-way driving problem, and more lives will be saved nationwide as a result.


Images: Finley Engineering Group; Icon by Freepik from

About The Author: Tappendorf is with Stanley Consultants and is a designer of the ADOT wrong-way driver alert system.