Mayor Wu Announces Expansion of Project Green Light Signal Optimization Program

Program has now retimed or coordinated more than 100 intersections across 20 neighborhoods

Today, Mayor Michelle Wu, the Streets Cabinet, and Innovation and Technology Cabinet announced the expansion of their partnership with Google Research to improve traffic flow in highly congested areas. The partnership, first announced last year, uses artificial intelligence to model traffic patterns and creates traffic signal timing recommendations for intersections experiencing congestion hotspots. Since April 2024, Project Green Light has analyzed traffic at hundreds of signalized intersections. The City has implemented Google Research’s recommendations to optimize 114 intersections across 20 neighborhoods including Brighton, Back Bay, North End, Roxbury, South Boston, Downtown, Fenway, Charlestown, Dorchester, Jamaica Plain, Mission Hill, South End, Hyde Park, West Roxbury, and the West End. This has led to an up to 33% reduction in unnecessary stops at certain congested intersections.

“The City of Boston is proud to partner with Google’s Project Green Light to mitigate the everyday headache of traffic and use AI to improve problem intersections,” said Mayor Michelle Wu. “Since the launch of this partnership, we have now retimed more than 100 intersections and will continue to explore innovative ways to make it easier and more efficient to get around Boston.”

“Project Green Light helps keep Boston moving safely by improving traffic flow and reducing delays at intersections,” said Jascha Franklin-Hodge, Chief of Streets. “It has been a highly effective tool, and we look forward to our continued partnership with Google to expand to even more intersections in the city.”

"What started as a pilot has now expanded into a practical AI tool supporting the City’s traffic engineers across every neighborhood," said Michael Lawrence Evans, Director of Emerging Technology for the City of Boston. "This collaboration allows us to respond more dynamically to changing traffic patterns, working alongside the Traffic Management Center's efforts to design and fine-tune signal systems throughout the city."

In 2023, Boston was ranked 8th in the world for highest traffic delays. Project Green Light, a Google Research initiative, uses AI and Google Maps driving trends to model traffic patterns and make recommendations for optimizing existing traffic light plans. By identifying potential adjustments in signal timing, Boston’s Traffic Management Center can improve traffic synchronization with nearby intersections or change “green time” between lights to better match demand. This adjustment of green light timing and coordination with nearby intersections means drivers now spend less time waiting through multiple signal cycles, both reducing how often they are starting and stopping driving and reducing overall traffic delays. 

The City of Boston has partnered with INRIX, a global leader in traffic analytics, to evaluate the impact of Project Green Light’s recommendations implemented by the Traffic Management Center. During phase 2 of the Project Green Light pilot, the City has seen an average 13.5% reduction in delay, with some locations seeing improvements of up to 24%, and a 20% average reduction of unnecessary stops across newly retimed intersections. At Atlantic Ave. and Richmond St. in the North End, the City saw a 21% reduction in overall traffic delay and a 33% reduction in unnecessary stops. Beacham Street and Maffa Way in Charlestown saw a 24% reduction in delay and 34% reduction in unnecessary stops after better coordinating this signal with those nearby. Project Green Light recommendations have been observed to be most effective during periods of heavy traffic, reducing delays when congestion is at its peak. 

Additional benefits include an average of nearly 4,000 gallons of estimated fuel saved over the course of a year per recommendation. At Beacham St. and Maffa Way, one of the intersections seeing the best results, drivers collectively are expected to save up to 14,000 gallons over the course of a year. The program has also helped the City engineers monitor traffic signal infrastructure by ensuring signal control boxes, copper/fiber-optic connections, and loop sensors are working properly.

Managed jointly by Boston’s Traffic Management Center and the Office of Emerging Technology, Boston’s use of Project Green Light complements existing work to keep our traffic signal network responsive to current traffic conditions. This fiscal year, the Traffic Management Center has implemented 81 traditional signal retimings and typically makes over 1000 real-time traffic signal adjustments every month.

Project Green Light is now live in 18 cities on four continents. Boston and Seattle are the only U.S. cities currently included in the program.

"Green Light reflects Google Research's commitment to advancing science and improving lives with AI. We're excited to continue partnering with Boston to help reduce emissions and make its streets more efficient,” said Matheus Vervloet, Product Manager, Google Research.

To learn more about this project, visit boston.gov/project-green-light.