Getting the green light

To a driver, few things are more frustrating than inching along on a freeway during rush hour. However, one of those few things may be hitting multiple red lights at busy intersections along an arterial route.

But like a tow truck in the rear-view mirror, help is on the way.

Researchers from the University of Minnesota, led by Henry Liu, have developed software designed to better manage the flow of traffic at intersections with stoplights. The software is the basis for SMART (Systematic Monitoring of Arterial Road and Traffic) Signal Technologies—a U startup company launched in 2011. 

With the new software, SMART Signal can directly retrieve traffic data from signal controllers without any additional hardware instrumentation, thus reducing time and costs. 

The Minnesota Department of Transportation (MnDOT) has installed the system at more than 100 intersections it monitors along busy trunk highways in the metro area, including Hwys. 10, 13, 7, 55, 65, and 61.

The advantages to the system are twofold, according to Heng Hu, the lead systems engineer for SMART Signal and a member of Liu’s research team for about six years.

“The system automates the data collection process at intersections and saves lots of time and energy,” he says. And it can “generate real-time arterial [road] performance measures,” so that traffic engineers can “observe” what’s going on along these critical traffic corridors.

The ultimate goal is to determine the queue length at stoplights and the total travel time—at a given time—along these corridors. Using this data, MnDOT can adjust the timing of traffic signals as needed to ensure speedier trips for motorists.

“Presently, our plan is to retime the signals in a corridor every three years, but this technology will help us determine whether that’s really needed,” says Steve Misgen, MnDOT metro traffic engineer. “For example, we might just need to retime the a.m. peak period, or maybe it can be done every four or five years instead. 

"I think it's a good relationship between the U of M theoretical researchers and the real world traffic operations personnel who run the signals,” he adds. “The operations personnel have gotten their input into the device, so we get exactly what we want—performance measures on our signals."

Where parallel lines meet

MnDOT is also supporting ongoing research utilizing capabilities of the SMART Signal software; namely, how it could be used as part of an integrated corridor management (ICM) system.

In this case, the system could diagnose a traffic incident on one road and help determine the capacity to handle automobiles on a parallel route. In the Twin Cities, a great model is the Interstate 394 and Hwy. 55 corridor west of downtown Minneapolis.

“If something happens on 394, we can decide how much traffic we can divert onto the parallel road—55,” Hu says. This system could help identify and predict the effects of rerouting travelers to the arterial road and then automatically adjust signal timing to compensate for the increased traffic.

And if all that results in a little less time in the car for motorists, everyone wins.

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