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We’re reducing emissions by optimizing signal timing in partnership with Google

A green traffic light shines in a black-and-white photo. A large building is in the background.
A green traffic light. Photo by Lucas Beck on Unsplash.

Blog stats: 500 words | 3-minute read


  • We’re working to reduce vehicle emissions, provide smoother travel, and use industry-leading technology through Project Green Light, in partnership with Google.
  • Using Google Maps driving trends to recognize inefficient signal timing, we receive detailed reports and recommendations on timing improvements to improve traffic flow and reduce stop-and-go conditions.
  • This project helps save engineering time and streamline our signal timing efforts, allowing for faster improvements by providing greater insights to build upon our typical review methods.
  • Seattle is the first North American city to partner with Google in this effort, along with other cities around the globe.
  • Early numbers from Project Green Light indicate a potential to reduce stops by up to 30% and reduce CO2 emissions by an estimated 10% at locations where it is implemented in participating cities, based on Google’s research.
  • You can read more about this project in articles by Geekwire and Wired, as well as a recent feature on CBS News.

Sitting at a series of red lights isn’t just frustrating – it can also lead to more stops and starts and increased carbon emissions which contribute to climate change. What if there were a better way to optimize travel using technology while helping the planet? Enter Project Green Light, which we’re partnering with Google on as the first city in North America.

Project Green Light provides a new, useful source of data to help us adjust the timing of Seattle’s traffic signals. Green Light scans congestion conditions using Google Maps driving trends, identifies where stop-and-go traffic may be due to inefficient signal timing, and provides a detailed report recommending timing improvements to make.

By offering a way to automate some manual tasks and provide greater data-driven insights, our team of experts in traffic management can more efficiently review and implement changes, allowing for more routine optimizations. We can also monitor the effectiveness of the change and, if needed, reverse the timing change.

View of the SDOT Traffic Operations Center, where our team monitors traffic conditions in real-time 24 hours a day. Photo: SDOT

In terms of locations in Seattle, we’ve adjusted signal timing along 15th Ave NW at NW Market St and NW 53rd St in Ballard, and at Greenwood Ave N and N 80th St in Greenwood. These locations were identified by Google and implemented by us as part of this partnership, based on the traffic trends analysis by Google.

Next steps

  • We plan to continue this partnership with Google as part of our overall efforts to address climate change and keep Seattle travelers moving safely and efficiently.
  • We’re also reviewing recommendations in Seattle’s SODO neighborhood and anticipate making signal timing adjustments in this area in early 2024.

Thank you for your interest, and please stay tuned for further updates as this work moves forward.