Project Green Light: Google Using AI for Sustainability
AI’s capabilities for improving sustainability goals are being unlocked more as it continues to evolve.
Urban infrastructure management is now gaining momentum as cities seek scalable solutions to environmental challenges without requiring substantial capital investment.
A perhaps less obvious use of AI for sustainability goals is the emergence of AI-driven traffic optimisation. This is a convergence of machine learning (ML) capabilities with existing municipal systems, offering immediate implementation potential through software-based interventions.
Google’s research division has demonstrated this approach through Project Green Light, expanding its AI-powered traffic optimisation programme to 70 intersections across 17 cities on four continents.
The initiative targets vehicle emissions at urban junctions where pollution levels reach 29 times those found on open roads, leveraging the company’s decade-long accumulation of global traffic data from Google Maps.
Project Green Light uses ML algorithms to analyse traffic patterns from Google Maps data, providing recommendations to city traffic engineers for optimising signal timing.
The system targets stop-and-go traffic, which accounts for half of all emissions at city intersections, through coordination of multiple adjacent signals rather than isolated optimisation.
What is Google’s Project Green Light?
The programme was born from Google Research’s 2020 exploration of climate mitigation technologies, initially considering diverse applications from cultivated meat to energy systems.
The pivot to traffic management reflected both the scale of the problem and the company’s unique data advantages in understanding global road networks.
“The goal is to reduce frustrating stop-and-go events, thereby cutting fuel waste and lowering emissions at intersections,” says Yossi Matias, Vice President and Head of Google Research.
Google Software Engineer Dotan Emanuel shares the ideas behind the project’s launch.
He says: “My wife said, ‘Why don't you do something about traffic lights? We stand at them for no good reason.’”
Road transportation contributes significantly to greenhouse gas emissions globally, with transportation responsible for 15% of total emissions.
At intersections, the problem intensifies as vehicles repeatedly accelerate from stationary positions.
“My initial thought was that we can't do anything about traffic lights,” Emanuel says. “But when it comes to research, the most fascinating challenges lie in the unknown.”
How does Project Green Light work?
The Google Research team identified that traditional traffic light optimisation required cities to install expensive hardware or conduct time-consuming manual vehicle counts – yet both approaches failed to provide complete information on traffic parameters needed for effective signal timing.
“We quickly understood we have a strong advantage that cities could benefit from — over a decade of Google Maps driving trends from across the globe,” Emanuel says.
The system creates an AI model that measures traffic flow through intersections, including start-stop patterns, average waiting times and coordination between adjacent signals.
The model then identifies improvements such as reducing red light duration during off-peak hours or synchronising previously uncoordinated intersections.
Green Light Programme Manager Alon Harris says: “In order to achieve a positive climate impact, we want to be able to deploy high-quality Green Light recommendations to many cities globally and scale fast.
“So we purposely set up everything to be simple and lightweight — cities don't need to invest in any dedicated software or hardware integrations.”
City engineers can implement the recommendations within five minutes using existing infrastructure and policies.
The system also provides a dashboard displaying city-specific recommendations with supporting traffic trend data and impact analysis reports after implementation.
Project Green Light expanding globally
Since pilot testing began in 2021, Google has deployed Green Light across cities including Rio de Janeiro, Seattle, Bengaluru, Boston, Haifa, Hamburg and Kolkata.
The programme now processes up to 30 million car rides monthly through its optimised intersections.
Early results indicate potential reductions of up to 30% in vehicle stops and up to 10% in emissions at treated intersections.
The system additionally coordinates multiple adjacent intersections to create sequences of green lights, further reducing stop-and-go traffic.
Commissioner of Police from Kolkata Vineet Kumar Goyal says: “Green Light has become an essential component of Kolkata Traffic Police.
“It serves several valuable purposes which contribute to safer, more efficient and organised traffic flow and has helped us to reduce gridlock at busy intersections.
In Manchester, England, the system provided insights for a network of 2,400 traffic signals.”
David Atkin, Analysis and Reporting Manager at Transport for Greater Manchester, adds: “Green Light identified opportunities where we previously had no visibility and directed engineers to where there were potential benefits in changing signal timings.”
Now, Boston – ranked eighth globally for traffic delays in 2023 – has implemented Green Light recommendations at more than 10% of its signalised intersections.
Alon says: “We offer each city dedicated reports with tangible impact metrics, such as how many stops drivers saved at an intersection over time.
“We think that's going to be a real incentive to not just implement the first recommendations, but also bring Green Light to more intersections.”
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