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Traffic signal goal is perfect timing

Chicago Tribune-April 17th 2006
Tara Leitzell says the traffic lights on Ogden Avenue in Chicago are timed so drivers hit every red light.

“Whoever did that has a special dislike for commuters,” said Leitzell, who drives from her home near Ogden and Chicago Avenue to her job at a medical center in Lawndale.

Chicago Transit Authority rider Betsy Roth complains that poorly coordinated traffic signals are at least partly responsible for CTA buses bunching up on Michigan Avenue in the 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 who lives in Lincoln Park. “Ten or 15 minutes later, three buses in a row show up.”

Who hasn’t been tempted to stomp off a bus that falls further behind schedule with every red light because it would be quicker to walk?

Or who hasn’t sat behind the steering wheel waiting at a red light late at night when no other moving vehicle is in sight?

Badly timed traffic signals rank among the chief traffic complaints of commuters and lead to frustration, gridlock, wasted fuel, worsening pollution, lost productivity and road rage.

The good news is that Chicago transportation officials at the Traffic Management Authority are focusing on solutions and new technology–as if timing were everything.

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.

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

Signal interconnects often include synchronization. But interconnects allow inclusion of cameras and sophisticated 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 percent improvement in travel times on corridors where signals are interconnected,” Montazery said.

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

Getting Around drove southbound on Michigan Avenue between Ohio Street and 16th Street during Wednesday’s evening-rush period. My speed in fairly heavy traffic ranged from about 10 miles an hour to 25 m.p.h., but the results were pretty good. I was able to hit as many as five green lights in a row.

The experience wasn’t as good driving northbound on State Street–against traffic lights favoring the southbound evening traffic flow out of the downtown. The travel time was longer than on Michigan due to a string of red lights a block apart encountered on the trip from 16th to Superior Street.

To balance out such situations, Chicago’s traffic management goal includes having the ability by the end of the year to remotely adjust the red-and-green cycles on about 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.

More changeable message boards are also being installed alongside some of the interconnected signals so motorists will be alerted before they get to the problem areas–and 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, meanwhile, is working to expand an experiment that started several years ago on a Pace bus route on Cermak Road in Berwyn and Cicero. Devices placed aboard buses extend the green-light time to permit buses approaching the intersection to make it through. The system has been particularly helpful in getting late buses back on schedule, officials said.

The CTA is 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.
The bus-priority system would help further shorten commuting times on Western, where buses on the CTA’s No. X49 Western Express route make limited stops, mainly at streets with connecting bus and rail lines on the West Side.

Pace has generated improvements in running times of 17 percent to 20 percent 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.

Pace is adding the bus-priority signal system on the Halsted Street corridor in the south suburbs near Harvey. The project might also be extended to Harlem Avenue in suburban and city areas, officials said.

“You get much better results when you have transit signal priority working in conjunction with coordinated traffic signals,” Bolton said.

In the suburbs, Lake County is leading the way in using intelligent transportation systems to relieve congestion and get the most capacity out of roads. 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 one day form a regionwide network.

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 heaviest.

Other types of “smart” traffic technology, however, still need some tutoring. In 2001, Chicago tested self-setting traffic signals at about a dozen River North intersections. The signals were designed to gauge congestion and automatically adjust based on the traffic flow.

But the experiment was stopped after several months because the system could not process the high volume of traffic data quickly enough to relay instructions back to the traffic lights in a timely manner, Montazery said.

“The concept is very promising, but there are still technology issues to be resolved,” he said.

The Chicago area, ranked No. 3 for traffic congestion in the U.S., is not alone in the struggle, although it appears to be ahead of many other metropolitan areas.

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 to simply respond to problems as 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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