Utah Department of Transportation and Matt Luker, UDOT’s statewide signal engineer
To create a peer-to-peer adaptive signal control system tailored to the fluctuating traffic volumes experienced by drivers on Main Street in Moab, Utah.
Moab is a tourist destination whose Main Street sees unpredictable traffic patterns due to tourist traffic that fluctuates at different times throughout the year. With a variable mix of local, truck, and tourist traffic, it has been hard to predict when intersections on Main Street will be hardest hit, and traditional timing systems have not been helpful. In the past, engineers would schedule special timing plans on weekends and holidays when heavy traffic would be expected, but they didn’t always guess right.
Adaptive control was an attractive option, but Moab is in a remote location far away from the engineers in Richfield (approximately 175 miles) and Salt Lake City (234 miles) who would need to operate the system. The solution needed to be easy to operate and capable of operating on its own with little intervention.
UDOT uses the latest generation of signal controllers, and new advancements allow UDOT to implement special programming that isn’t possible on older controllers. Matt Luker developed programming for the Moab system that utilizes controllers and detectors that are already in place. He created a peer-to-peer system that relies on data from SmartSensor Matrix to adapt signal control to existing conditions.
Peer-to-peer systems look at whether cars are being detected during the green phase. Moab’s system counts every tenth of a second and classifies the time as “used” or “unused” green time. The measured value is then compared to an ideal value, and if there is more dead time on the detectors than expected, then it knows that less green time was required during that cycle. On the other hand, if the detectors are occupied more than predicted, then it is assumed that more green time is required. Data from the last three cycles are averaged out and the next cycle will allow more green time, and so forth, increasing or decreasing green time to what is needed.
UDOT uses the latest generation of signal controllers, and new advancements allow UDOT to implement special programming that isn’t possible on older controllers.
The system has improved traffic flow on Main Street by increasing the amount of green time for those movements when traffic is there to use it. When traffic dies down, the cycle length comes down to reduce delay for pedestrians and cross-street traffic.
Despite significant benefits, the Moab system cost very little to implement because the peer-to-peer system does not require a server, and UDOT was able to take advantage of controllers and detectors that would have been installed anyway. Typical adaptive systems can be costly; the Federal Highways Administration estimated that adaptive systems can cost up to $65,000 per intersection. UDOT was able to outfit seven intersections on Main Street at a fraction of that cost.
Because of the cost savings and traffic improvements, UDOT awarded the Moab peer-to-peer system the agency’s 2016 Innovation Award, in recognition of its contribution to UDOT’s mission to “find new and better ways to do more with less.”
