Traffic engineer Mike Bertolini studied a computer screen featuring the aerial view of the Forest Park Parkway/Skinker Boulevard intersection.

"This is our big headache intersection," he said. "This is the entrance to the city, the exit from the city. It's over capacity."

The traffic operations center — equipped with flat-screen television monitors and multiple maps of St. Louis streets — was created during the buildup to the Highway 40 (Interstate 64) closure. Many feared that rebuilding a highway through the heart of the region would lead to traffic jams on St. Louis-area side streets.

Those fears quickly evaporated, in part, because of regional efforts to coordinate traffic signals on streets people used as detours. Despite the signal-timing improvements, traffic planners say there is still more work to do to keep St. Louis-area traffic signals in sync.

For instance, the region's three-year spending plan for roadwork includes millions to pull together more signals in St. Louis, St. Louis County and St. Charles and Jefferson counties, and to add other equipment to make traffic flow better.

Until then, some motorists will continue to see red while waiting for signals to turn green.

Charlie Dahlheimer, a downtown St. Louis resident, says traffic signals along 18th Street tend to favor northbound or southbound cars — even when traffic is light. The waits are so long that he made a U-turn last week rather than wait to cross the street.

"If you hit 18th Street when it is turning red, you have to make a decision to either run the darn thing or wait for a long time," he said.

Dahlheimer and other frustrated motorists have regularly sought answers from local transportation officials on the weekly Road Crew chat on STLtoday.

Traffic coordination has been a long-standing problem in the city, he said. There were problems years ago when the city tried to accommodate traffic in and out of the city on Gravois Road.

"The problem is not new," Dahlheimer said. "But the technology that is there that should solve it wasn't there 50 years ago."

Bertolini gets frequent backlash from drivers over the Forest Park/Skinker intersection, which is part of its coordinated system. There's just too much traffic converging on one intersection, he said. That was particularly true while the eastern half of Highway 40 was closed between Interstate 170 and Kingshighway for much of 2009.

Kingshighway, which is also synchronized, poses similar challenges.

Because of the heavy demand by pedestrians wanting to cross the street, the city's timing plan has to build in blocks of time for them to safely cross the street at numerous locations.

"I don't want people to have the convenience of driving through the city at the expense of someone's life trying to cross the street," Bertolini said.

how it works

To better understand how traffic signals are synchronized, it is probably best to think of them as a series of stopwatches, each one set at 100 to 140 seconds, depending on traffic volumes. That is how long it takes for the typical intersection to cycle through the green, yellow and red lights in each direction.

Each one has a timing plan depending on the time of day.

During morning rush hours in St. Louis, the timing plan generally begins at 5:30 and ends at 9:30. The timing plan for the evening rush generally runs from 3:30 to 6:30 p.m. The rest of the time, the plan accounts for a normal balanced flow of traffic.

When one traffic light in a synchronized series turns green, Bertolini said, the next one down the line is typically set to turn green a short time later. Say 10 seconds. The next one after that is set to turn green a short time after that, and so on.

The series of stopwatches is generally coordinated by one central timepiece.

The lights are timed in a coordinated progression to accommodate a group of cars that traffic engineers refer to as a platoon. The idea is to keep the platoon moving in an efficient manner — limiting the amount of time those cars sit idling at red lights.

Bertolini figures about 75 percent of the city's traffic signals are part of the current network. He estimates that within 10 years, the remainder should be online. The city is currently installing fiber optic cables downtown, to synchronize major east-west streets west of Tucker Boulevard.

In west St. Louis County, the Missouri Department of Transportation coordinates hundreds of traffic signals from a massive traffic command center. St. Louis County also maintains a traffic nerve center.

At the MoDOT center, agency staff can monitor dozens of intersections on such major state routes as Manchester Road, Highway 141 and Page Avenue.

It's a daily balancing act, said Greg Owens, a MoDOT traffic operations engineer in the St. Louis area. One of the biggest obstacles is the overall capacity of a road. If there aren't enough lanes to pump traffic through, traffic signal timing won't solve the problem.

He estimates that about 80 percent of the traffic signals on state-maintained thoroughfares are part of MoDOT's coordinated system. Few additional signals will be added to the network.

Instead, future upgrades will include adding surveillance cameras along Highway 141 between Highway 40 and Gravois Bluffs. Electronic message boards soon will be fired up along Lindbergh in south, west and north St. Louis County.

Owens said traffic signal coordination was not well understood.

To traffic planners, a 10 percent reduction in travel time and delay is "wildly successful," he said. Reducing the amount of time cars idle at traffic signals helps save gas, reduce tailpipe emissions and tamp down driver frustration.

But that does not mean that a driver will encounter an endless string of green lights, he said.

"Everybody would like their light to be green," Owens said. "I'm no different. I'm out there driving, too. But the problem with the traffic signal is that somebody's green light is (someone) else's red light."