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Why is it so hard for Baltimore to synchronize its traffic lights? Here’s what we found.

Editor’s note: This is the latest in a series of occasional articles inspired by readers’ curiosity. What do you wonder about the Baltimore area that you’d like us to investigate? Tell us at

Ron Legler sees drivers run red lights in Baltimore all the time on his daily commute between his home in Canton and his job as president of the Hippodrome Theatre on Eutaw Street downtown.


He almost doesn’t blame them.

“Every time it turns green," Legler said, “the next light turns red.”


When that happens, Georgia Martin, an accountant who lives in Federal Hill, often finds herself sitting stopped at green lights. Frustrated drivers try to pull through the intersection, she said, blocking crossing traffic when the light does change and worsening the problem.

“Blocking the box, in Baltimore, is a way of life,” she said. “I don’t know why [the lights] don’t turn green at the same time."

So why is it so hard to synchronize Baltimore’s traffic lights? It’s a perpetual question for drivers — and one that came up more in The Baltimore Sun’s reader-inspired series than almost any other. We asked city officials and outside experts to find out.

The red-light-green-light scenario Legler and Martin describe is a result of any number of factors, according to city transportation officials, including the time of day and the intersections in question, disruptions such as crashes and road closures, driver behavior, speed-calming measures — and, in particular, a lack of investment in Baltimore’s antiquated, 15-year-old network of traffic lights and traffic management technology.

A matter of timing

Baltimore’s downtown lights are programmed to operate differently at different times of the day. The main routes into and out of downtown, including President, Fayette, Conway, Pratt and Lombard streets, are favored over smaller side streets in the morning and evening rush hours, and the pattern is adjusted to accommodate traffic flows for special events such as Orioles and Ravens games and concerts.

While drivers and bus passengers might be desperate for a consistent row of green lights, the traffic lights are timed to make sure the downtown roads don’t become highways.

“The timing progression is set at a rational speed,” said Frank Murphy, the Baltimore Department of Transportation’s deputy director, who has worked there for decades. “If they go too fast they’ll hit a red, if it’s timed properly.”

But proper timing is not a given.


More than a quarter of the city’s 1,300 traffic signals are not designed to connect to the city’s traffic management system, running on timers alone and requiring the public to call 311 to report outages or other problems because the system cannot control them remotely, said Raj Sharma, deputy chief for signals and a 20-year veteran of the Department of Transportation.

Of the other 974 traffic signals designed to connect to the system, he said, only about half actually do.

“With the current system, we don’t have that much flexibility, [like] what a new system would provide, like an adaptive system or the smart signals,” Sharma said. “The system is old, and we’ve been keeping it up."

That means it’s up to Reggie Coates, the control system operation supervisor, to run the show each day.

From the city’s Traffic Management Center in Mount Vernon, Coates acts as the eyes and ears of the city — monitoring traffic cameras and answering 311 calls, dispatching crews to fix traffic light power outages and other snags, and referring all sorts of other issues to the appropriate agencies.

“[When] you think transportation, you think about traffic only,” he said. “But we get all kinds of calls for trees being down, debris in the roadway, and stuff like that. And then it switches over to another department, but we have personnel out there to respond, to mitigate whatever the situation is.”


‘It’s a Rubik’s cube’

Even the most sophisticated software cannot take every factor into account, said Jeffrey Buckholz, a traffic engineering consultant in Jacksonville, Florida, who has been in the industry for 40 years.

Managing an entire city’s worth of traffic is complicated and requires a lot of trial and error, daily monitoring and periodic updates as traffic patterns evolve with cities’ development over time, he said.

“It’s a tougher nut to crack than most people would think,” Buckholz said. “It’s a Rubik’s cube to get this thing to work right.”

Traffic engineers typically give what he calls the “domino greens" to the heaviest-trafficked streets they want to prioritize, seeking to avoid backups on freeways and main arteries, while keeping wait times for pedestrian crossings and side streets as reasonable as possible, he said.

“You’ve got to do what’s best for most of the people,” Buckholz said.

The city’s traffic priorities are changing, too. Under the new Complete Streets law, transportation officials must design streets to prioritize pedestrians, bicyclists, transit and other modes of transportation over the single-occupancy vehicles that currently dominate streets.


Synchronizing the traffic lights isn’t necessarily the solution to decreasing congestion, said Hesham A. Rakha, the Samuel Reynolds Pritchard professor of engineering at Virginia Tech, whose doctoral thesis focused on traffic signals and who teaches a 14.5-week course on the topic each semester.

Traffic-responsive signal controllers, which adapt to real-time traffic conditions instead of operating on a series of daily peak patterns, allow signals to skip unnecessary light phases, according to a study Rakha performed in partnership with Morgan State University’s National Transportation Center. So if there are a bunch of cars backed up at a particular intersection, the light is more likely to turn green.

Researchers developed the controllers and tested them in Blacksburg, Virginia, and Los Angeles. They reduced backups by up to 77% at isolated intersections, and reduced delays by up to 67% across a network, according to the study. Vehicle emissions were lowered by at least 6% in both cases.

“What we’ve shown is having them run each independently is actually better,” Rakha said. In Baltimore, “they’re using an archaic, pretty old kind of approach. ... It doesn’t mean what they’re doing is wrong, but there are now opportunities with more advancements, you can do better than that.”

The biggest difficulty in solving traffic congestion in general is anticipating how people will adjust their behavior to any new traffic patterns, he said.

“It’s a chess game,” Rakha said. “Every time I make my move to change conditions, the drivers adjust to what I do. I have to anticipate how they’re going to adjust.”


‘Drivers will notice’

Officials say some relief is on the way.

The city plans to spend more than $25 million, including state and federal funding, over the next five years to overhaul its traffic management system, upgrade technology and replace dozens of traffic lights and cameras.

That amount is "more than we’ve spent on our signal system than I can recall in my career in one time,” DOT’s Murphy said. “What that says is that the DOT considers having the signal system working well a priority.

"That wasn’t necessarily always so years ago.”

In a $4.5 million timing-optimization project, city transportation officials will study morning, midday and afternoon traffic patterns at 1,100 intersections across the city and compare the data they collect to the traffic models the department currently uses to time the lights, Murphy said.

City officials will use the new data to tweak the traffic light timing as needed, beginning with downtown intersections next fall.


“That’s where drivers will notice,” Murphy said.

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The city will spend an estimated $9 million to install 28 new traffic signals over the next two years; $4.5 million to overhaul the existing traffic management system software; and another $4.5 million to install new fiber-optic cables that will replace 40-year-old copper wiring to give the system more bandwidth.

It will spend another $2.7 million to replace 23 traffic cameras, add eight new ones, and install a video management system that will allow officials to rotate the cameras from the traffic control center and collect better footage. That project, expected to be awarded in May, will fix the electrical wiring of 56 traffic lights, which will help prevent the flashing lights often caused by wear and tear on the wiring.

Six other new cameras — three on Interstate 83, two on Russell Street, and one at Conway and Howard streets — will give officials better eyes on three of the most heavily trafficked areas of the city, allowing them to better monitor accidents, lane closures and other issues.

The need for investment was highlighted last summer, when as part of the “Don’t Block the Box” campaign under Mayor Catherine Pugh in 2018, officials shortened the timing of the light phases at 13 downtown intersections to try to prevent traffic from backing up to the previous intersection. The effects rippled to more than 60 total intersections, and the results were disastrous.

“Whenever you mess with one, you affect all the rest,” Murphy said.


Exasperated drivers must keep in mind that keeping traffic moving efficiently through a busy downtown area is a complex task, Rakha said.

“If it wasn’t complicated," he said, “we’d have solved it a long time ago.”