Timing is everything when it comes to traffic signals

News Chicago Tribune April 19, 2006
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Many Chicago drivers have noticed that traffic lights on streets such as Ogden Avenue are timed so drivers will hit every red light.

Chicago Transit Authority (CTA) rider Betsy Roth believes that poorly coordinated traffic signals are partly responsible for CTA buses bunching up on Michigan Avenue downtown.

“If I miss my bus I can look up Michigan and see a caravan of buses going a block, stopping at red lights, going another block and stopping again,” said Roth, a marketing executive. “Ten or 15 minutes later, three buses in a row show.”

Many commuters are tempted to get off a bus as it falls further behind schedule with every red light because walking would be faster. And many drivers have been stuck waiting at a red light late at night when no other vehicles are driving in sight.

Poorly timed traffic signals rank among the chief traffic complaints of commuters and lead to frustration, grid lock, wasted fuel, worsening pollution, lost productivity and road range, the Chicago Tribune reported.

According to the newspaper, Chicago transportation officials at Traffic Management Authority are focusing on solutions and new technology for better timing.

By the end of 2006, about 60 more intersections will have signals that are interconnected and synchronized with other nearby signals, according to Yadollah Montazery, assistant director of the city’s Office of Emergency Management and Communications, which oversees the Traffic Management Authority. The upgrade will bring the total to about 460 intersections in the city of Chicago, the Tribune reported.

Synchronization involves sequencing the traffic lights to maximize traffic flow through a series of green lights. Nearly 2,000 of Chicago’s 2,800 signalized intersections have synchronized traffic lights, according to the Tribune.

Signal interconnects often include synchronization, but interconnects also allow for the inclusion of cameras and technology to monitor and improve in real time how well an intersection is working because the traffic signals are physically linked by fiber optic cables.

“Typically we have seen a 15% improvement in travel times on corridors where signals are interconnected,” Montazery said.

The federal government is aware of the tremendous benefit of interconnecting traffic signals, which is why it provides cities with 80% of the funding for design and construction, he said.

Chicago’s traffic management goal includes have the ability by the end of the year to remotely adjust the red-and-green cycles on 200 of the existing 400 interconnected signals by using cameras positioned above the streets and computers inside the traffic authority’s headquarters in the West Loop, the Chicago Tribune reported. Changeable message boards are also being installed alongside some of the interconnected signals so motorists will be alerted before they get to problems areas and can take alternate routes.

Montazery said being able to adjust traffic signals in response to situations, rather than changing signal timings only at predetermined hours each day, will improve traffic flow around accidents, crime scenes and special events.

The CTA is working to expand an experiment that started several years ago on a Pace bus route on Cermak Road in Berwyn and Cicero, the Tribune reported. Devices placed aboard buses extend the green-light time to permit buses approaching the intersection to make it through. The system has been helpful in getting late buses back on schedule, officials said.

The CTA is currently studying several corridors for its pilot project. Officials have tentative plans to test the bus-priority signal system on portions of Western Avenue, said CTA spokeswoman Noelle Gaffney.

Pace has seen improvements in running times of 17% to 20% since it began using the bus-priority system, which sends an optical signal to traffic lights, said Michael Bolton, deputy executive director of strategic services. The improvement has contributed to rider increases on the route, he said.

In the suburbs, Lake County is using intelligent transportation systems to relieve congestion and get the most capacity out of roads, the Tribune reported. The county launched a $7 million system in February to interconnect traffic signals along state, county and municipal roads.

The Illinois Department of Transportation is working with Cook, DuPage, Will and Kane Counties to develop similar systems that could eventually form a region-wide network, according to the newspaper.

Approximately 100 of Chicago’s 2,800 signalized intersections are equipped with actuated signals, said Brian Steele, spokesman for the Chicago Department of Transportation. Actuated signals use sensors buried in the pavement to determine how much red, green and green-arrow time to give based on where the traffic flow is the heaviest.

The Chicago area ranks third for traffic congestion in the U.S and is not alone in the struggle. A recent survey gave poor grades to the efficiency of the nation’s traffic signal operations. More than two-thirds of the traffic agencies surveyed in 49 states said they either had no management plan for their traffic signal operation, or their plan was simply to respond to problems after they occur. Fifty-seven percent said they don’t routinely review traffic signal operations to determine whether changes are needed based on residential or commercial development patterns, according to the survey conducted by the Federal Highway Administration and other transportation groups.

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