City of Boston Partners with Google on Traffic Signal Optimization

Today the City of Boston, Streets Cabinet, and the Innovation and Technology Cabinet announced a partnership with Google’s Project Green Light team to optimize traffic signal timing and improve traffic flow in highly congested areas. The technology uses AI to model traffic patterns and creates signal timing recommendations that can reduce stop-and-go traffic and emissions. In 2023, Boston was ranked 8th in the world for highest traffic delays. Through this partnership, the City has implemented four recommendations at intersections in Fenway-Kenmore, Mission Hill, and Jamaica Plain by changing signal timing.

“One of the most frustrating parts of living in a major city is traffic, so Boston is taking every step to combat congestion and get people to where they need to go,” said Mayor Michelle Wu. “We often find that small traffic hotspots from mistimed signals or curbside issues can swell into larger congestion, so targeting these micro spots goes a long way. This innovative work with the latest technology from Google’s Project Green Light will help relieve the frustrating congestion that so many of our residents face, while helping to reduce emissions and inefficiencies on our city streets.”

For the past five months, Project Green Light has analyzed traffic at hundreds of signalized intersections using AI and Google Maps driving trends to provide recommendations for optimization of traffic signals and patterns. The Boston Transportation Department’s traffic engineers assessed each recommendation for safety, feasibility, and effectiveness to determine if the recommendation could be implemented. Once implemented, Project Green Light then measures the impact on traffic patterns and provides this analysis to BTD to continue monitoring for any future needed changes. 

Since the partnership began in February 2024, BTD’s traffic engineers have used Project Green Light’s recommendations to optimize signal timing and reduce unnecessary stops. At the intersections of Huntington Ave. & Opera Place and at Amory Street & Green Street, stop-and-go traffic has been reduced by over 50%. Cities around the world that use Project Greenlight have experienced a 10% average reduction in emissions. 

“We hear from residents throughout the city that traffic can be stressful and takes time away from family, friends, and work,” said Jascha Franklin-Hodge, Chief of Streets. “Project Green Light provides a powerful tool that helps us optimize traffic flow on our streets. It provides our traffic engineers with important data to tweak a signal by seconds which can help reduce congestion along a corridor. We look forward to continuing this partnership as one way to help our streets work better for everyone. ” 

"We are just starting to realize the potential of machine learning and AI in some of the City's core operations," said Michael Lawrence Evans, Director of Emerging Technology for the City of Boston. "Our partnership with Google's Project Green Light team demonstrates how this technology can have an immediate impact on a common experience like traffic congestion, while paving the way for continuous improvements across our traffic signal network."

Green Light, a Google Research initiative, uses AI and Google Maps driving trends to model traffic patterns and make recommendations for optimizing the existing traffic light plans. They then identify adjustments to traffic light timing to improve the efficiency of an intersection, such as improving the synchronization between lights at nearby intersections or shifting "green time" between lights to better match demand. BTD engineers are considering more recommendations from Project Green Light to be implemented throughout 2024. The program has also helped the City monitor traffic signal infrastructure by ensuring signal control boxes, copper/fiber-optic connections, and loop sensors are properly working.

Project Green Light is now live in 14 cities on four continents. Boston and Seattle are the only U.S. cities included in the program.

“Through Project Green Light, we are using AI to help improve the lives of people in cities around the globe by reducing traffic and emissions,” said Matheus Vervloet, Product Manager at Google. “The success of Green Light is only possible thanks to the partnership we have with cities like Boston. We're encouraged by the initial results we’ve seen in Boston and look forward to working closely with the city to scale this technology to more intersections.”