Arizona DOT installing new sensors to help track Phoenix’s freeway traffic flow


The Arizona Department of Transportation (ADOT) is moving closer to completing installation of a new network of in-pavement sensors that will monitor traffic flow along key stretches of Phoenix-area freeways.

In addition to helping ADOT track real-time freeway conditions, the sensors provide the data used to estimate the travel times that are displayed for drivers on dynamic message signs (DMS) above freeways. The data also helps ADOT and the regional transportation-planning agency, the Maricopa Association of Governments, make decisions about future freeway improvements. Using electronic wires embedded in the pavement, the sensors have been used along many valley freeways for years. The current project is installing additional in-pavement sensors as a more reliable replacement for the legacy acoustic devices that are mounted on poles.

The deployment of the new electro-magnetic sensor loops is expected to be completed by this summer. The project is one way ADOT is working toward the agency’s continuous improvement goal of reducing congestion on freeways in the metropolitan Phoenix region.

After installing in-pavement sensors on Interstate 10, US 60 (Superstition Freeway) and State Route 51 (Piestewa Freeway) in recent months, ADOT will address Interstate 17 over the next several weeks, starting with the southbound lanes between Peoria Avenue in north Phoenix and 19th Avenue south of the downtown area. When the sensor-installation project is completed, more than 85 locations on Phoenix-area freeways will have new traffic-flow sensors.

ADOT is also working on an ongoing project to put a fresh layer of rubberized asphalt on a busy stretch of Interstate 17 in Phoenix. The rubberized asphalt used by the agency on many highway paving projects not only creates a smooth ride for drivers, it also provides a second life for the rubber from thousands of old, worn tires that might otherwise be dumped in landfills. Rubber from about 75,000 tires will be used in the layer of asphalt being added to 11 miles of I-17 between Dunlap and 19th avenues in Phoenix. Rubberized asphalt has also been recognized for reducing traffic noise, specifically the sound from vehicle tires, by approximately four decibels in neighborhoods near urban freeways.

“What we like most about rubberized asphalt is its durability,” said Dallas Hammit, ADOT’s state engineer and deputy director for transportation. “When our riding surface pavement lasts longer, in some areas for well over a decade, it is cost effective and limits traffic disruptions.”

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About Author


Tom has edited Traffic Technology International (TTi) magazine and its Traffic Technology Today website since May 2014. During his time at the title, he has interviewed some of the top transportation chiefs at public agencies around the world as well as CEOs of leading multinationals and ground-breaking start-ups. Tom's earlier career saw him working on some the UK's leading consumer magazine titles. He has a law degree from the London School of Economics (LSE).