City works with Purdue to create high-tech traffic-control system

July 2, 2012  


Bullock traffic flow

Darcy Bullock, from left, a Purdue professor of civil engineering, and former postdoctoral research associate Edward J. Smaglik, discuss information provided by detection equipment at an "instrumented intersection." The research aims to improve the safety and efficiency of traffic flow. (Purdue News Service file photo)


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WEST LAFAYETTE, Ind. - Purdue University engineers have worked with the city of Lafayette, Ind., to create a new "Advanced Transportation Management System," a network of sensors, computers and software to efficiently control traffic signals and reduce congestion.

The system is one of the first deployments in the country of new traffic signal management techniques developed at Purdue, said Darcy Bullock, a professor of civil engineering and director of the Joint Transportation Research Program at Purdue.

It allows engineers to attack traffic jams on two fronts: Determine more precisely how to adjust the length of green signals to better match traffic volumes, and synchronize signals in series on busy roads so that motorists catch green lights in sequence.

 "We have all been at intersections where the green light did not last long enough for all the traffic to pass through and then seen drivers on the opposing side of the intersection get too much green time," Bullock said. "What we are doing enables electronic signal controllers to collect data that can be used to effectively alter this timing to better manage traffic flow."

The system improves signal-timing efficiency, said Lafayette City Engineer Jennifer Miller.

"The ultimate goal is to allow the majority of the traveling public to spend less time stopped at a signal when it is red," she said. "Other potential benefits are improved fuel efficiency and reduced emissions because less time idling reduces fuel usage and the associated emissions. Having fewer starts and stops also reduces fuel consumption and emissions."

The system is integrated into signal controllers that are widely used at intersections across the country and uses specialized software algorithms. Data are displayed on a main computer in the city's traffic center, allowing personnel to monitor information and make a change to individual intersection timing.

"It is like a dashboard for signal systems," said Neal Carboneau, implementation manager for the Joint Transportation Research Program. "You could equate it to the leap from horse-drawn carriages to commercial aircraft. In the past, you had to manually count vehicles and time their progression through the corridors. You'd have to come back to the office and do calculations, then return to the signal to make adjustments to improve the flows. Then, in order to verify that the changes were effective you would need to go through the same procedure again. As you can imagine, it was a very inefficient and time consuming process."

Recent advances in technology, including improvements to the reliability and speed of Internet access, as well as greater computer storage and processing ability, have made it practical to use computerized systems that operate signals.

"Induction loops" in the pavement near signals indicate that a vehicle is in the turn lane and other locations. These loops, which are ubiquitous in U.S. cities, are connected to a computer in a cabinet at each intersection.

Algorithms in the system use mathematical equations and data from the loops and other sensors to determine whether an intersection's traffic volume is exceeding its capacity, tracking traffic during each cycle of green-amber-red. The resulting information is plotted on graphs that show how many vehicles are unable to get through an intersection before the signal turns red.

Such data enable the system to identify needed changes to signal timing to facilitate the flow of traffic and also to synchronize signals.

"How often have you driven down a corridor and had it go green, green, green, green?" Bullock asked. "The answer is, not very often. The problem is that until now we have not had good measurement tools needed to create patterns of sequential green signals."

The system incorporates new "traffic signal performance measures," criteria based on research on traffic flow that enable computers to identify the need for signal timing optimization. The performance measures were developed at Purdue in collaboration with the National Cooperative Highway Research Program and the Indiana Department of Transportation

"We've married some theory with new data collection practices, performance measures and modern IT technology to come up with a better tool for making decisions about signal management," Bullock said.

Loop detectors are used in combination with the new algorithms to upgrade standard electronic controllers, the brains of traffic-signal systems at intersections.

"The system has been installed and is operational, but since it is the first of its kind, getting it to be fully functional will take some time," said Fred Koning, foreman in the Lafayette Traffic Department.

Having a centralized system is helpful in troubleshooting the network, which is made up of numerous signals and computers and a web of electrical cables and sensors, Koning said.

"Several other states and local agencies across the country are considering modeling their system specifications based upon the system in Lafayette," Carboneau said.

The project has involved about a dozen Purdue faculty, staff and students from the School of Civil Engineering

"The Indiana Local Technical Assistance Program supports research and helps transfer technology from research to implementation in line with Purdue's strategic plan for discovery with delivery," Carboneau said. "They were integral in their support of the research and facilitation of the dialogue between the city, industry and Purdue, assisting in the system's development and operation."

Jay Grossman, a project engineer, and others from Elkhart County, Ind., assisted the research, and provided guidance in the development of specifications used in the procurement of the system. Elhart County is in the process of bringing a similar system online.

Recently receiving a Merit Award for the new system from the American Council of Engineering Companies were Miller, Koning and Thomas Vandenberg from the engineering firm Butler, Fairman and Seufert Inc.

Previous research has been funded by the Indiana Department of Transportation. A portion of that earlier work, on State Road 37 in Noblesville, Ind., yielded data indicating a potential 20 percent decrease in travel time for drivers. Findings from a recent report about the Noblesville research show that optimizing signal timing resulted in an estimated annual cost savings of $472,817, with a reduction in carbon dioxide emissions of 197 tons per year showing the financial and environmental benefits of using systems and processes such as these.

"Not only are there benefits in improving he efficiency of the local agency's personnel, but there are also benefits that decrease the travel time, vehicle cost and emissions of the traveling public," Carboneau said.  

Writer: Emil Venere, 765-494-4709, venere@purdue.edu

Sources: Darcy Bullock, 765-494-2226, darcy@purdue.edu

               Neal S. Carboneau, 765-496-7435, ncarbo@purdue.edu

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