Keeping Boston Intersections Moving During High Traffic

April 1, 2015

For those who think the traffic signals in Boston work in some sort of random, mechanical fashion, look up at the cameras on about every intersection – smile big – and think again.

High up on the seventh floor of Boston City Hall, a well-publicized, but still mostly unknown, Traffic Management Center (TMC) monitors some 550 of the City’s 847 signalized intersections six days a week using high-tech computer equipment, numerous observation screens and the expertise of a handful of experienced traffic engineers. Their work keeps things flowing when the computer models that control most of the City’s intersections don’t jive with the conditions on the ground, using “tweaks” here and there that tend to make a difference in the larger picture of moving vehicles in and out of Boston.

“In today’s world, I would be surprised if most big cities don’t have something like this,” said John DeBenedictis, director of engineering for the Boston Transportation Department (BTD). “A lot of people may think traffic lights change randomly from red to green to yellow. We do have some controls and many other cities do also have that…Hopefully, with what we can do here, we can make a 5 to 10 percent difference in the flows of traffic. We have about 58 percent of the signalized intersections that are on the system. They are all primarily in the Mass Ave area, though we do have many main thoroughfares in the neighborhoods tied into our system.

“In the last 25 years, we’ve been expanding this,” he continued. “You can’t widen the roadways here to add capacity, so we try to monitor traffic in real time to improve the conditions on the ground.”

In what looks like a serious weather-monitoring center or a high-stakes “war room,” the TMC does battle with back-ups on weekdays from 7 a.m. to 10 p.m. and on Saturdays from 9 a.m. to 5 p.m. with a rotating crew of about 10 engineers.

Yes, they can change a light from red to green, or green to red, at the click of a mouse.

And yes, they can watch that happen in real time on the numerous screens displaying key junctions throughout the city.

However, rarely are such magical tactics used.

Mostly, traffic engineers in the TMC use software, a network of cameras and thousands of on-the-scene traffic sensors to monitor in real-time the various intersections – looking for alerts or indicators on giant digital maps that tell them where the problems exist. Then, after looking at the situation via a camera, they can prescribe a change in the timing of the lights. Sometimes they might move to a “rush hour” program for an intersection early in the day when things have unexplainably gotten very busy.

After about four of five minutes of the “tweak,” most of the time things begin to smooth out, and the engineer can put the light back on its programmed computer model.

“Even if you have a lot of back ups, fairly small changes and tweaks in the system can have a significant impact over time,” said Don Burgess, a supervisor at the TMC. “It’s a lot like the cashier lines at the grocery store. If you’re short a cashier and a wave of customers come, then this line starts to build up and it takes forever to get through. If you could become aware that there is a problem about to happen, and add one extra cashier before the line forms, you avoid the back up. It’s a slow process that we rely upon, and over a period of time, the processes and changes can help things keep flowing.”

As Engineer Keith Bynum monitored Boylston Street recently, he noted that one has to take a long view of the situations and there is likely never a time when clicking the “green light” button can help.

“Our changes can make a difference, but it doesn’t happen right way,” he said. “If you add three or five seconds on an approach for five minutes, that can help clear out the intersection. Over the course of an hour, it could be the difference between being clear every light cycle or having buildup to the next block.”

The worst times, both said, are in the summer on Thursday afternoons. Even more than on July 4th, those days can try one’s patience.

“July 4th isn’t as bad because it’s all in one location and people expect it to back up,” Bynum said. “Thursday afternoons in the summer can be bad; it’s really all or nothing on those days. Most of that has to do with the regional highway system. If you can’t get on the highway, then you can’t get through our intersections…It’s really the things that are out of the ordinary that can be tough. On Winter Vacation Week this February we had shows at the TD Garden during the day and snow everywhere and those things all merged to give us a real headache.”

Burgess added that in the fall near the colleges and universities, traffic could also be challenging.

“In the fall, the college areas get kind of crazy,” he said. “The college kids come to Boston for school and initially think they can all drive their cars anywhere at any time like they did in their small towns. After a few months, they realize that they can’t and either don’t drive as much or start taking the MBTA. However, it really is the unusual stuff that we concentrate on.”

The TMC was last updated around 2004, DeBenedictis said, and now has control over about 550 intersections. Central computers and human observers can see, control and intercede in the workings of all of those lights directly from the TMC.

Burgess said the program began in the 1970s as a trial run using newfound computer technology. It was an innovative effort and proved valuable enough to stick around and get bigger.

“We used a computer system along Mass Ave and that was our first trial,” he said. “It was only 18 intersections back then and there were no cameras.”

Slowly but surely, the TMC has expanded greatly over time – especially in the last 10 years when its gone from 12 cameras in 2000 to around 250 today.

DeBenedictis said they take every opportunity the can to lay their cables under the street and install cameras at intersections. The most expansive and difficult part is to get the cables underground and hooked into the TMC communications system.

Often, he said, they’ll take advantage of a reconstruction project to expand into key areas of the neighborhoods. One example of that is on Dorchester Avenue in Dorchester where the TMC expanded out several miles when that roadway was reconstructed – now allowing them to control the signals there.

Even with expansion, there is only so much that can be done.

DeBenedictis and Burgess said that during this year’s record snow, there were times when they saw that the intersections couldn’t be helped, and police officers had to be called in to move traffic and calm the nerves of drivers stuck in complete gridlock.

But even in those situations, the TMC proved helpful in being able to spot bad intersections and prioritize them for snow removal crews.

“We were able to compile a list of hot spots for the snow removal crews to get to at night,” said Burgess. “That allowed them to set priorities and make a real difference, and it just goes to show another way this system can be helpful.”


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