Adaptive Signal Control: The End of Long Traffic Lights?

Roads in U.S. cities aren’t getting any less congested. While more and better public transportation is one obvious answer, the Federal Highway Administration (FHA) is encouraging another solution: controlling traffic lights with computers to keep the traffic moving.

Adaptive signal control technology (ASCT) uses strategically placed sensors that measure traffic volumes in conjunction with mathematical algorithms that calculate the best timing for switching signals from red to green. While several other countries have embraced it, the United States has been slow to catch on. If the FHA has its way, that may change.

Boston recently announced it will move to an ASCT system as part of its Go Boston 2030 action plan, which focuses on improving all parts of the city’s transportation infrastructure. City engineers are currently studying traffic patterns in certain areas as a prelude to finalizing the system’s design. Then they’ll test it in a few neighborhoods that suffer from long backups, like the Seaport District, before they take it citywide.

In promoting ASCT, the FHA cites studies that show it can improve average performance metrics such as travel time, emissions and fuel consumption by at least 10 percent and in some cases as much as 50 percent. It notes that ASCT can be especially helpful in reducing congestion caused by traffic accidents, special events and road construction.

Boston isn’t the first U.S. locale to implement ASCT. Oakland County in Michigan, for example, has been successfully using it since 1991 and now has it installed on more than half its signals. Austin, Texas, and Portland and Bellevue in Washington state have also been leaders in adopting this tech solution.

Why haven’t more metro areas gone this route? According to the FHA, one of the biggest barriers is the fact that very few traffic agencies currently collect data on the effectiveness of their traffic signal systems. If transportation departments don’t have that data, they can’t grasp how much better ASCT would be.

There are several variations of ASCT systems, and manufacturers and researchers are constantly searching for ways to improve them. A few years ago, professors at MIT in Boston studied traffic patterns in Lausanne, Switzerland, and developed a new way to compute optimal traffic light timing. Caroline Osorio, the chief researcher, said simulations demonstrated their method could cut average travel time for commuters by 22 percent and dramatically reduce the amount of carbon emitted by vehicles idling at red lights. New York City has been testing the method to see if it can help the city better manage its traffic during rush hours.

If cities and their surrounding metro areas find ASCT systems can work that effectively, travel-weary commuters are likely to embrace them wholeheartedly.

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Mary Lou Jay is a freelance writer who has been covering business and technical developments in the residential and commercial construction industries for more than 25 years.