Dust storms—caused when dust particles raised by the wind create rolling dust clouds—have become increasingly common in Arizona. While dust-related weather events were once associated with summer monsoons, in the past 10 years the season for these storms has extended into the fall. Occurring with little forewarning, dust storms are quick-moving and can reduce visibility to less than 300 feet, resulting in dangerous driving conditions.
In the Grand Canyon State, the deadliest portion of I-10 in relation to dust storms stretches from Sunshine Boulevard to Picacho Peak Road in Pinal County, where much of the land is used for agricultural purposes. Dust storms along this corridor have led to more than 50 crashes and eight total fatalities since 2000. Currently, sections of I-10 experience as much as 40% truck traffic and by 2040, traffic volumes along the corridor are expected to more than double. Since trucks drive much of the economic movement in Arizona, closures due to crashes can have a significant financial impact. To address these concerns, the Arizona Department of Transportation (ADOT) has partnered with Kimley-Horn to construct safety improvements along the corridor in a project that is the first of its kind nationwide. With funding from the Highway Safety Improvement Program and the Fostering Advancements in Shipping and Transportation for the Long-term Achievement of National Efficiencies (FASTLANE) grant, ITS infrastructure will be installed to improve safety and traffic management during low visibility events attributed to dust.
Read on to learn from project manager John Kissinger, P.E., PTOE, Tom McCullough, P.E., and Brenda Soto how Kimley-Horn is deploying technologies for real-time monitoring of weather conditions, activating a warning system for drivers, implementing lowered speed limits during dust events, and employing other advanced approaches to mitigate dust-related collisions.
Dynamic Message Signs (DMS)
In addition to the traditional uses of DMS including for AMBER Alerts, crash/hazard warning messages, and PSAs, this project will use DMS to post advisory or control messages that alert travelers of dust conditions. ADOT currently has three DMS mounted on overheard structures and four more will be added to cover the westbound and eastbound directions at the beginning, middle, and end of the corridor. All the DMS will be integrated into ADOT’s Camera Cameleon software, allowing the ADOT Traffic Operations Center (TOC) to operate and monitor them.
Variable Speed Limit Signs (VSL)
For the first time in Arizona, VSL signs will be used. The new signs will replace static speed limit signs within the I-10 project limits and will be installed on both sides of the road. Consistent with ADOT’s current placement of static speed limit signs, VSL signs will be installed at each freeway on-ramp to notify incoming drivers of the speed limit. At entrances to the corridor in both directions, a series of VSL signs will be installed in 1,000 feet increments to facilitate reductions to the speed limit, which will decrease by 10 mph at each sign until a speed of 35 mph is reached. Like the DMS, these signs will be connected to ADOT’s existing Camera Cameleon system for monitoring from the TOC.
Closed-Circuit Television (CCTV) Cameras
Five CCTV cameras will be placed within the project limits to provide complete visual coverage. Each CCTV camera can cover at least one mile in either direction. CCTVs will be monitored by operators from the TOC and will provide lines of sight to the DMS so that messages can be verified visually.
Weather Detection Stations
A long-range detection device will be used to detect approaching dust conditions. Using X-band radar technology, this device will scan the horizon with a range of 40 miles for approaching visibility issues and will allow ADOT to provide advanced notification to travelers and reduce speed limits to prepare for oncoming dust events. In addition to the long-range detection device, spot detection devices will be used to detect dust conditions and will be spaced consistently across the project area to detect and calculate a visibility measurement. Based on the presence and scatter of particulate matter at the device location, these measurements will indicate how far a traveler would be able to see during low visibility conditions.
Loop Detector Stations
From Sunshine Boulevard to Picacho Peak Road, loop detector stations will be installed in the pavement in each lane in both directions. To collect speed, occupancy, and volume data for the ADOT TOC to monitor, these detectors will be placed where the DMS are located. Like the other loop detectors throughout Arizona, these new devices will be integrated into ADOT’s traffic management system, so data is transmitted to the TOC.
To connect all the ITS devices to the TOC, new fiber and conduit infrastructure will be installed along one side of the highway through the project area. Devices that are located on the opposite side of I-10 from the backbone communication infrastructure will be connected by communication run across the roadway.
Systems Operation Overview
When dust is detected by spot detectors, a notification will be sent to the ADOT TOC. An operator will then confirm road conditions using the CCTV cameras. Speed limits displayed on VSL will incrementally reduce along the corridor until a speed of 35mph is reached. DMS will show advanced warning messages to notify travelers.
Takeaways and Potential Future Applications
During the summer and fall months, dust storms along I-10 can arise with little warning and pose major safety concerns. Advanced technologies including spot detection and remote sensing technology will measure visibility along the corridor and identify approaching dust conditions. To reduce the chance of dust-related collisions and more safely manage traffic during dust events, VSL signs and DMS will warn travelers of actual or potential dust events prior to encountering them within the corridor. ADOT will be provided with valuable information about traffic management, maintenance, and operations, and will help advance research and the application of similar systems in other locations impacted by low visibility events.