The Virginia Department of Transportation (VDOT) is testing an adaptive traffic signal system at five intersections on Braddock Road, between Route 123 and Burke Station Road.
Four cameras have been installed at each of five Braddock Road intersections. According to Michael Clements, the VDOT traffic systems manager in charge of the project, the cameras work with sensors already embedded in the road.
Northern Virginia’s 1,500 traffic signals operate on time of day plans, with at least eight and as many as 16 in place for each signal.
According to Clements, adaptive timing is based on demand and fluctuations in patterns during real time.
For example, if there is a special event at George Mason, the cameras "see" what’s happening and a plan to ease traffic can be generated on the fly, Clements said. Each signal “talks” to the next signal, like traffic cops with walkie talkies, to move the traffic along on a green band.
Traffic in the pilot corridor was measured in May for the “before” part of the test, and will be evaluated in September for comparison. "Engineers want to know whether there were improvements in traffic flow, whether travel time was decreased, and whether there were fewer stops,' Clements said. All this while striving to “do no harm” to traffic on the side streets. "The adaptive system can easily be switched off at any time if there is a problem," Clements said.
So far, Clements has heard the system is working “real well.” By one measure, the backup at Braddock Road and Route 123 has gone from two miles to three-quarters of a mile.
One engineer told Clements that he can’t ever remember traveling that stretch of Braddock Road without stopping at a red light, but he has been able to get through on all greens since the switch.
Clements expects the improvements to continue even as summer vacation ends and classes resume at George Mason. “Braddock Road will remain heavily congested during the peak morning and afternoon rush hours, but the adaptive system should shorten the amount of time the corridor is congested and allow for quicker recovery," he said.
Decreased travel time should continue after rush hour as well, with fewer stops at traffic signals along Braddock Road and shorter delays for motorists on side streets. Clements said other benefits include reduced gas consumption because of fewer stops and starts, and fewer rear end collisions.
The Braddock Road trial is one of 11 in the state's $3 million InSync pilot program. The InSync system was developed by Rhythm Engineering. It's use began at the end of July along Brddock Road.
Elsewhere in the region, the system is being tested in the Warrenton area with good results, Clements said. It is scheduled for testing at 13 intersections along Route 1 in Prince William County beginning in October.
Clements is “a firm believer” in the adaptive system, and says it’s now a matter of seeing how well it works. “We’re trying to use technology to solve some of our congestion problems instead of adding lanes,” he said. “If it works it’s going to save us a lot of money.”