An automated system that adjusts the timing of traffic signals when buses are running late is helping to improve transit reliability along Langston Blvd.
Since late summer, county transportation officials have been using “transit signal priority” along the 5-mile corridor from East Falls Church to Rosslyn. The system extends green lights and shortens red lights when ART buses are behind schedule — resulting in a small but measurable impact.
“The goal is smarter, more reliable transit,” said Josh Drucker, transit-technology manager for the county government, at the Nov. 18 meeting of the Transit Advisory Committee.
About 30 traffic lights along Langston Blvd are equipped to receive signals from buses and react accordingly. The primary local bus running in the corridor is ART 55, which carries about 1,000 travelers per day.
“As a passenger, you probably won’t notice anything different,” Drucker said. “We’re only talking seconds, but seconds matter.”
The goal is to improve on-time performance by 1% to 3%. In the early months of the effort, before tweaks were made, the improvement resulted in about a 0.5% improvement.
“We’ve turned this on, now we’re massaging it,” said Kirk Dand, another transportation planner.
In October, on-time performance on ART 55 was 80% and the countywide average was 77%. Being too aggressive in giving buses priority could compound overall traffic congestion, Dand said.
“We’re finding that sweet spot, optimizing the system,” he said. “It’s not like ‘set it and forget it.’”
Evaluation of the project’s impact is slated for the spring.
The project comes amid a region-wide effort to improve transit ridership by making buses move more quickly. “This is not the silver bullet” but represents “part of the solution” in improving on-time reliability, Drucker said.
County transportation planners aim to extend the technology to the Columbia Pike corridor next year, once roadwork is substantially complete. Additional future corridors could include Glebe Road, Washington Blvd and Crystal City/Pentagon City.
Eventually, the initiative could expand to include Metrobus and other transit systems that operate in Arlington.
John Carten, who chairs the Transit Advisory Committee, said a coordinated effort would be very helpful.
“System optimization is so important,” he said.
Drucker seemed to agree.
“It’s been a slow project, but a very exciting project,” he said.
