CMU develops high-technology traffic signal timing system
East Liberty pilot project hailed for cutting travel time, emissions
September 25, 2012 12:00 PM
Jared Cohon, president of Carnegie Mellon University, stands near as Henry Hillman speaks about CMU's first-of-its-kind traffic signal control system. A pilot project for the synchronized signals reduced vehicle wait time in the high-traffic sections of East Liberty by 40 percent. The event was held in front of the Target store near Penn Avenue and Penn Circle.
By Don Hopey Pittsburgh Post-Gazette
Tired of sitting in long lines of traffic, burning gas, and wasting time commuting through Pittsburgh?
Carnegie Mellon University has developed a first-of-its-kind traffic signal control technology that automatically adjusts and coordinates signal timing to accommodate varying traffic volumes and has shown strong promise for reducing commuting times and vehicle emissions during a pilot trial at nine intersections in East Liberty.
At a news conference Monday in East Liberty next to one of those intersections, CMU researchers said the smart traffic signal system, in place since June, has reduced vehicle wait time on Penn Avenue, Penn Circle South and Penn Circle East, by an average of 40 percent. Travel time through the area declined by 26 percent and vehicle emissions are down an average of 21 percent.
CMU video demonstrates success of stoplight synchronization
A first-of-its-kind traffic signal control technology has shown promise in reducing pollution and commuting time during a pilot trial in East Liberty. (9/24/2012)
The next step is to demonstrate the technology on a wider scale by doubling the size of the pilot project area.
City leaders and researchers say the intent is to deploy the system citywide, possibly in five years, and export the technology to other cities that have shown interest.
PG graphic: Smart traffic signals (Click image for larger version)
"The idea is to optimize the movement of traffic through each intersection, and the results have been startling," said Allen Biehler, a executive director of CMU's University Transportation Center and former state secretary of transportation. "I've already talked to people in Philadelphia and Chicago, and they are very interested.
"If we are able to make this relatively low-cost system work in the complex street system of Pittsburgh it could be very exciting and very important for traffic flow and for encouraging new business to locate in the city."
Developed through CMU's Traffic21 Initiative, the adaptive signal system is much more complex than existing synchronized signal systems that are pre-programed to regularly flash green lights along a main artery, like Fifth Avenue in Oakland.
The CMU system uses cameras or in-road sensor "loops" to sense traffic volume at each intersection, said Stephen Smith, director of the Intelligent Coordination and Logistics Laboratory in CMU's Robotics Institute. Using concepts from the fields of artificial intelligence and traffic theory, the system fine-tunes green light lengths in real time to best accommodate vehicle flow, and relays those changes in real time to system sensors at neighboring intersections in the urban street grid.
"It's unique because each intersection controls itself and then communicates with its neighbors," Mr. Smith said. "And it can be expanded incrementally, intersection by intersection."
Pittsburgh Mayor Luke Ravenstahl said the pilot's success was a breakthrough that could make the city's traffic system work more efficiently and reduce the need to do expensive road widening or eliminate on-street parking to facilitate traffic flow.
The first, nine-intersection phase of the CMU traffic signal pilot program cost $150,000 and was funded by three local foundations, the Henry L. Hillman Foundation, the Heinz Endowments, and the R.K. Mellon Foundation, all members of the Breathe Project, a coalition of 112 organizations and 1,200 individuals focusing on improving the region's air quality.
Philanthropist and business leader Henry Hillman praised the technological breakthrough and said it presents an opportunity for Pittsburgh to take an international leadership position in "demonstrating how low-cost, easy-to-implement technological solutions can reduce traffic congestion, vehicle fuel consumption and emissions while also improving safety and air quality."
"We saw the adaptive signalization project as a way to reduce the estimated 17 percent of our local air pollution problem that comes from vehicle emissions," said Robert Vagt, Heinz Endowments president. "What we discovered from this great result is that something done with the intention of improving air quality can also deliver a significant economic benefit."
Stan Caldwell, deputy director of CMU's Technologies for Safe and Efficient Transportation program in the University Transportation Center, said the planned expansion of the adaptive traffic signal program in East Liberty is necessary to show it works in complex urban street grid systems.
"The bigger we can do it and the longer it goes on, the more confident that people will be in adopting the technology," said Mr. Caldwell, adding that it's already affecting his travels in the area.
"There was a time when I would never travel through East Liberty because of the traffic," Mr. Caldwell said. "Now it's not so bad to go through that area."