Mercer SCOOT

Updated: August 23, 2019

What’s happening now?

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 for the last month and results are positive. In the eastbound direction, during the 3-hour evening peak period, people driving are moving an average of 2.7 minutes faster and experiencing a 38% increase in travel time reliability.


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 of where Mercer SCOOT is.


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 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.

Mercer SCOOT information graphic from June 2019
Information graphic from June, 2019





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.


Greg Spotts, Director
Address: 700 5th Ave, Suite 3800, Seattle, WA, 98104
Mailing Address: PO Box 34996, Seattle, WA, 98124-4996
Phone: (206) 684-7623

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The Seattle Department of Transportation (SDOT) is on a mission to deliver a transportation system that provides safe and affordable access to places and opportunities for everyone as we work to achieve our vision of Seattle as a thriving, equitable community powered by dependable transportation.