Link to Transportation Home Page Link to Transportation Home Page Link to Transportation About Us Page Link to Transportation Contact Us Page
Delivering a first-rate transportation system for Seattle Scott Kubly, Director







Site Index

Mercer Corridor Project

Last updated: August 30, 2017

We're working to make travel along Mercer St more reliable by making our signal system smarter. The project is part of our Intelligent Transportation Systems Program. We've been testing it through July and results are positive. In the eastbound direction, during the 3-hour evening peak period, people driving are moving an average of 6.2 minutes faster and experiencing a 33% increase in travel time reliability compared to before SCOOT installation. Were tracking results monthly, see below.


We've installed a new system along Mercer St between 3rd Ave W and I-5 that coordinates traffic signals to help keep people driving moving. The system, called "SCOOT" (Split Cycle Offset Optimization Technique), is the first in Seattle. In total, 32 signalized intersections use SCOOT.


Map - click to view larger


SCOOT provides significant benefits:

  • Quicker, more reliable travel times through the network
  • Enhanced transit operations
  • Reduced overall emissions and fuel consumption
  • Effective management of traffic fluctuations due to special events

How it Works

SCOOT works in real-time to reduce delays and adapt to changing traffic volumes, such as congestion caused by nearby sport or concert events. The system detects cars in each lane at every intersection. It determines traffic levels, predicts the flow of traffic, and adjusts the amount of time available to each movement through the intersection. The result is more effective and responsive signal operations.

SCOOT Display - SCOOT in action in SDOT's Transportation Operations Center.
SCOOT in action in SDOT's Transportation Operations Center.

To assess the how well SCOOT is working, vehicle data is being collected daily and compared to historical averages. Reporting periods include morning and evening peak travel times (3 hours) in both the eastbound and westbound directions during the 5-day work week. These periods are when traffic volumes are at their highest. From the data received to date, the following changes have occurred.

July 2017

Infographic: July 17-21, 2017

April 17 | April 24 | May 1 | May 8 | May 15 | May 22 |  May 29  |  June 5 |  June 12 |  June 19 | June 26 | July 3 | July 10 | July 2017


The Mercer Corridor stretches from Interstate 5 to 5th Ave. W, and has been one of the City of Seattle's most significant transportation challenges for over 40 years. SDOT is committed to improving the Mercer Street Corridor. Learn more about what we've done over the past few years.


John Marek,, 206-684-5069

Home | About Us | Contact Us | Site Index | News | FAQs | E-Mail Alerts