by Blake Herzog
A one-of-a-kind dust detection system is up and running along 10 miles of Interstate 10 in Pinal County to issue warnings and adjust speed limits for drivers caught in one of the sudden, often monsoon-driven desert dust storms that can slash visibility to zero in seconds.
The stretch runs between Eloy and Picacho, an area that has seen multiple dust storm-related fatalities over the years.
The Arizona Department of Transportation has installed a series of electronic signs every 2 miles between mileposts 209 and 219, which can reduce the speed limit from 75 mph to 35 mph, depending on current and forecast weather conditions.
This section will be bookended by conventional road signs warning drivers they are entering a “variable speed limit corridor.” Adjusted speed limits will appear and overhead message boards will issue storm-related warnings to drivers when they’re activated.
Less obvious components of this complex system include 13 sensors that use light beams to measure the density of dust in the air. Once the readings reach a certain density, the speed limit and road warning signs will be triggered, adjusting the speed limit to the severity of the storm.
“All components of the system are existing and proven technologies. ADOT’s innovation is tying everything together as a system that works automatically. And there are a lot of technologies: visibility sensors, a weather radar, variable speed limit signs, speed feedback signs, pavement sensors to monitor real-time traffic flow, overhead message boards and closed-circuit cameras,” ADOT spokesman Garin Groff said.
The technology is monitored by ADOT’s Traffic Operations Center in Phoenix, where staff can see real-time information on conditions such as the speed and flow of traffic. Closed-circuit cameras provide visual confirmation of conditions along the roadway and in the distance.
Groff said the system underwent a 30-day test period before going live June 15, the official start of the Arizona monsoon season. Software was used to simulate the conditions of a storm and the equipment performed as expected, with the session cut off just before the signs would have activated and given drivers a false alarm.
The entire system costs about $6.5 million and was funded in part by a $54-million federal FASTLANE grant ADOT received for I-10 projects that widened sections between Eloy and Picacho. This pilot project will advance the state’s knowledge of whether similar technologies would be effective along other Arizona highways.
Regardless of any current or future warning systems, highway users are urged to stay off the roads when there’s a possibility of encountering severe weather. Those who are caught in a dust storm should exit the road at the next available opportunity, or else pull to as far off the paved roadway as possible and turn off all vehicle lights.
For more tips on how to react to a dust storm on the road, see ADOT’s www.pullasidestayalive.org.
