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Liu Gets SMART About Traffic Signals
 Liu stands beside a controller used to test his
SMART-Signals system. Green lights usually mean go when traveling in a car, but congested intersections often have drivers only seeing red. It’s a rampant problem plaguing roadways across Minnesota and the country that’s had no insightful means of diagnosis – until now. For the first time, Civil Engineering Assistant Professor Henry Liu and his SMART-Signals data collection system are attempting to untangle snarled traffic by analyzing the interaction of vehicles and intersection traffic signals.
The name SMART-Signals is short for “Systematic Monitoring of Arterial Road Traffic Signals.” The two-year program sponsored by the University, the Minnesota Local Road Research Board, Hennepin County, and the U.S. Department of Transportation shows the promise of examining the process of traffic congestion in unprecedented detail. “This project has a lot of potential,” said Liu. “It’s probably the Nation’s first in terms of this scale of data collection and high-resolution data.” Liu believes the key to unclogging congestion lies in looking at the coordination between incoming traffic and intersection signal timing.
To figure out the best balance between green light length and the amount of incoming traffic, engineers really need to know when and how many cars cross intersections. Right now, control cabinets cannot record the number of cars tripping loop detectors or seen in camera systems. For his SMART-Signals project, Liu developed a device for use in controller cabinets capable of counting cars while also recording the traffic signal’s current phase. “We’ll know when a phase started, ended, when a vehicle crossed through the intersection, and over time how many vehicles passed by,” said Liu. “Anything related with input into the intersection is recorded as an individual event and archived.” In theory, Liu’s system should give engineers the revealing data they need to prescribe the right timing schedules for individual traffic signals.
To test his system, Liu required a stretch of roadway with two particular traits: First, the road needed to have a mix of features, such as varying spacing between traffic lights and differing densities of traffic along its length. Secondly, and understandably most critically, the street had to have existing traffic problems.
The researcher chose to trial his system along a notoriously clogged transportation artery in Edina, Minn. “It’s a very, very congested corridor,” explained Liu. Located on a three-mile stretch of France Avenue, the experimental area has 20 intersections fed by everything from quiet neighborhood side streets to a roaring interstate freeway.
Hennepin County was already aware of France Avenue’s snags and hitches so it hired a traffic consulting firm to re-time the strip’s traffic lights. Now, the county plans to use Liu’s system to measure and verify the effectiveness of any changes made along the route. To accommodate the modern recording equipment, the community agreed to replace antiquated hardware inside controller cabinets along the route. The upgrades give Liu the signal input and connections his devices need to collect meaningful data and transmit it by modem back to the University campus.
The combination of Liu’s clever SMART-Signals system, a perfect test site, and a cooperative governmental partner offer a fortunate chance for unprecedented insight into traffic’s worst problem. With more drivers on the road than any other time in human history, congested intersections will continue to clog commutes. The system might just be what drivers need to see not only green lights again, but happily the open road too.
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