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Center for Transportation Studies

New SMART Signal installation helps MnDOT monitor timing plans

smart signalResearchers from the U of M recently developed a new version of software for the SMART Signal system, and deployments at more than 50 intersections managed by the Minnesota Department of Transportation (MnDOT) are already under way.

SMART Signal (Systematic Monitoring of Arterial Road and Traffic Signals) automatically collects and processes data from traffic signal controllers at multiple intersections. It then creates performance measures, including information on the times and locations congestion occurs on a roadway. The system was originally developed by civil engineering associate professor Henry Liu to improve traffic management on urban arterial streets. Funding for the system’s development was provided in part by the ITS Institute.

With the new software, also developed by Liu and his research team, SMART Signal can directly retrieve traffic data from signal controllers without any additional hardware instrumentation—reducing both the time and cost associated with implementation.

The new software has been incorporated into the iMonitor system currently offered by Smart Signal Technologies Inc., a startup company launched in 2011 to commercialize the SMART Signal system.

Recently, MnDOT had the iMonitor system installed at several intersections on Trunk Highway (TH) 10 and TH 65. According to metro traffic engineer Steve Misgen, MnDOT plans to equip additional intersections on TH 61 sometime this fall, for a total of more than 50 new intersection implementations.


The new installations are allowing MnDOT to monitor existing signal timing plans and evaluate their performance by providing data on queue length, level of service, travel time, speed, volume, and delay, Misgen says. In addition, several of the new installations support MnDOT’s signal timing consultant, Alliant Engineering, in its collection and analysis of traffic data.

“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. For example, we might just need to retime the a.m. peak period, or maybe it can be done every four of five years instead,” Misgen says.

In addition to these ongoing implementations, MnDOT also continues to support research related to the SMART Signal system. In the latest MnDOT-funded study, Liu and his team investigated how SMART Signal could be used as part of an integrated corridor management (ICM) system.

The proposed ICM system would use the performance measures generated by the SMART Signal system to diagnose incidents on signalized arterials and propose new signal control strategies that could be deployed in real time to mitigate traffic congestion.

The system also aims to reduce overall network congestion by using the available capacity of parallel routes—for example, by rerouting traffic from a freeway to a parallel signalized arterial during times of peak traffic congestion or when a crash occurs. In this case, SMART Signal could help identify and predict the effects of rerouting travelers to the arterial and then automatically adjust signal timing to compensate for the increased traffic.

The study tested the proposed ICM system using a traffic simulation model based on the I-394 and TH 55 corridor in Minneapolis. Results showed that the system significantly reduces network congestion—the average delay and number of stops per vehicle was reduced and average vehicle speed increased.

“The ICM control system developed in this project has a very promising future for real field implementation,” Liu says. “We look forward to testing the field performance of the proposed approach in future projects.”

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