U.Va. Research Aims to Optimize Traffic Light Timing to Reduce Gas Consumption and Emissions

April 29, 2008 — With gasoline prices soaring and emissions raising concerns for the environment, the timing of traffic signals could provide some relief on both counts, according to research being conducted by Byungkyu "Brian" Park, an assistant professor in the University of Virginia School of Engineering and Applied Science.

Working with team members at the Korea Transport Institute and Virginia Tech, Park is examining the way that traffic signal control systems can not only streamline the flow of traffic to reduce congestion, but also can help reduce both fuel consumption and emissions.
The optimization of traffic signals dates back to the late 1950s and early 1960s, Park notes. But it was based on a macro-level model because of limits to computing speeds.

Today, Park and his colleagues are able to base their research on individual vehicle movements rather than the overall flow. That permits them to get accurate data on fuel consumption and emissions.

"We use very high-fidelity microscopic traffic simulation tools. Once we have this, we can evaluate the performance of any existing traffic light control system," Park said. "We can then optimize traffic signals to maximize fuel efficiency and lower emissions, or to minimize delays. When we maximize for fuel efficiency, we do see slightly more queues and higher travel times.
The key is to create a pattern that allows drivers to maintain similar speeds. "If everyone were moving as a train, instead of switching lanes and trying to beat red lights, everybody would be OK," Park said.

Park and his team have begun an additional study on the role that enforcement plays, creating models based on drivers' desired speeds. If the speed limit is, say, 45 miles per hour, some drivers may choose to go as fast as 55. That means there is a 10-mile-per-hour distribution of desired speeds between 45 and 55 that the optimized traffic signals must take into account.
"But it you tell drivers that they can go up to 50 miles per hour without being arrested for speeding, but anything above that will be enforced, you can reduce the distribution of desired speed to 5 miles per hour," Park said. "So if you can assume a higher enforcement rate or a better compliance rate, it may be possible to achieve both the fewest delays and the best fuel consumption."

Park is backed by a well-established research center — the Center for Transportation Studies — as well as an exceptional team of academic colleagues. His team consists of his former U.Va. Ph.D. student, Ilsoo Yun, now a researcher at the Korea Transport Institute, and Kyoungho Ahn, a senior research associate at Virginia Tech.

The Center for Transportation Studies, launched in the late 1940s by the U.Va. Engineering School in partnership with the Virginia Department of Transportation's Virginia Transportation Research Council, aims to "produce outstanding transportation professionals, conduct innovative research with actionable results and provide public service." Over the years it has added partners such as the U.S. Department of Transportation and the National Science Foundation.

Park has found a niche with traffic signal research — science that is immediately relevant to people who are working toward an environmentally sustainable future. With partnerships in government and academia, it has the potential to be implemented on a large scale and significantly improve the environment. 

— By Zak Richards

About the University of Virginia School of Engineering and Applied Science

Founded in 1836, the University of Virginia School of Engineering and Applied Science combines research and educational opportunities at the undergraduate and graduate levels. Within the undergraduate programs, courses in engineering, ethics, mathematics, the sciences and the humanities are available to build a strong foundation for careers in engineering and other professions. Its abundant research opportunities complement the curriculum and educate young men and women to become thoughtful leaders in technology and society. At the graduate level, the Engineering School collaborates with the University's highly ranked medical and business schools on interdisciplinary research projects and entrepreneurial initiatives. With a distinguished faculty and a student body of 2,200 undergraduates and 700 graduate students, the Engineering School offers an array of engineering disciplines, including cutting-edge research programs in computer and information science and engineering, bioengineering and nanotechnology.