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I-5 - NB Seneca to SR 520 - Mobility Improvements


April 2017

  • WSDOT engineers have completed design work for this project, but there is no funding for construction work.
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This project has been shelved until funding is available for construction. When construction begins, contractor crews will improve the mobility along a 2.51-mile stretch of northbound Interstate 5 from Yesler Way to Lakeview Boulevard through Seattle. Crews will:

  • Add an additional lane between the Seneca Street off-ramp and the Olive Way off-ramp by replacing existing barriers, rails and curbs with a thinner barrier, reconstructing asphalt shoulders with concrete and restriping the roadway.
  • Install ramp meters on the collector-distributor on-ramp and the Cherry Street on-ramp.
  • Install nine new sign bridges, along with updated signing.
  • Extend Active Traffic and Demand Management (ATDM) system north to State Route 520.

Why is WSDOT improving the mobility of this section of northbound I-5?
This section of I-5 carries approximately 50,000 vehicles a day and includes a two-lane stretch that creates one of the worst traffic bottlenecks in the state. Traffic often backs up to Boeing Field and there are many congestion-related collisions throughout the day.

A third lane will be added through the current two-lane bottleneck after the Seneca Street off-ramp. This third lane will be an extension of the existing Seneca Street exit only lane and will be HOV only, except for vehicles exiting at Seneca Street.

In order to create a seamless transition to the existing four lanes of traffic after the Cherry Street on-ramp, a right, auxiliary lane will be added from the Cherry Street on-ramp and end as an exit only lane at Olive Way.

What are the challenges we face?

  • Road and ramp closure planning: Keeping traffic and the economy moving during construction are some of our top priorities. Our planners work with local cities, agencies and transit providers when planning closures. They also consider traffic volumes while balancing that against the time necessary to complete the work. Work hours may still inconvenience some drivers, but WSDOT tries to strike a balance between both the needs of drivers and completing the work successfully.
  • Road repairs: Removing existing barriers and pavement can sometimes reveal problems in the roadbed underneath such as deep cracks or potholing. Problem areas will need to be addressed.
  • Utility conflicts: Utility companies may need to move power, telephone, cable and/or fiber optic lines in order for contractor crews to complete mobility improvement work.

What should drivers expect?
To avoid disruption of the high daytime traffic volume on I-5, there will be mainly nighttime single lane closures and flagging in the work zone.

The End Result
This mobility improvement work is projected to reduce travel times by up to three minutes on weekdays and weekends. High-occupancy vehicles will benefit with an additional bypass lane on the mainline and collector-distributor on-ramp. The extended ATDM system is expected to reduce collisions by providing drivers with information about what to expect as far as congestion and/or incidents ahead.

Project Benefits

  • Improved safety: Extending the northbound I-5 ATDM system to SR 520 is expected to reduce collisions by providing drivers with information about what to expect as far as congestion and/or incidents ahead.
  • Congestion relief: After completion of the project, travel times are projected to decrease by up to three minutes.

What is the project timeline?
WSDOT engineers have completed design work for this project, but there is no funding for construction work.

Financial Information

Financial Data for PIN 100521W, 100521X
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $2,765
CWA $0
Total $2,765

Project signage will reflect the cost of construction engineering, project bid award and sales tax.

The total estimated cost for this project is $20.08 million. Planning and design ($2.77 million) were funded through a Puget Sound Regional Council (PSRC) grant and Pre-Existing Funds (PEF). There is no funding yet for construction ($17.31million).

How can I get more information?
Justin Fujioka

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