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

Project news

  • Work began in June 2021.
  • People traveling northbound I-5 between Seneca Street and SR 520 or the northbound collector/distributor at night should plan for lane and ramp closures.
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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:

  • Crews will move existing barrier and restripe northbound I-5 to make the freeway three lanes between Seneca and Cherry streets. Currently this area has two lanes after the exit-only lane at Seneca Street; the exit-only lane will become a through lane. 
  • Install ramp meters on the collector-distributor and Cherry Street on-ramps.
  • Install nine new sign bridges, along with updated signs.
  • Add signing to display lane closures.

This section of northbound I-5 carries approximately 100,000 vehicles a day and includes a two-lane section 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.

Crews will replace barrier near the existing Seneca Street exit-only lane and restripe to create three through lanes at the current two-lane bottleneck after the Seneca Street off-ramp. This third lane will be open to all vehicles and for those exiting at Seneca Street.

To create a seamless transition to the existing four lanes of traffic after the Cherry Street on-ramp, crews will add an auxiliary lane from the Cherry Street on-ramp, which will end as an exit only lane at Olive Way.

What should drivers expect?

Work will be mainly nighttime lane closures in the work zone to avoid disrupting high daytime traffic volume on I-5.

The end result

This mobility improvement work is projected to improve traffic flow and reduce congestion delays. All vehicles will benefit with an additional lane on the mainline and collector-distributor on-ramp. 

Needs & benefits

  • Improved safety: Creating three through lanes is expected to reduce collisions by providing drivers with information about what to expect as far as congestion and/or incidents ahead.
  • Congestion relief: Traffic flow through the area should improve and reduce congestion delays.


  • Fall 2020: Advertise for competitive bids
  • June 2021: Begin construction
  • Fall 2022: Complete construction


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) $23,848
CWA $0
Total $23,848

This project received construction funding in the 2017-2019 transportation budget.

  • Planning and design ($2.77 million) were funded through a Puget Sound Regional Council (PSRC) grant and Pre-Existing Funds (PEF).
  • Construction ($17.74 million) was funded through federal and state Pre-Existing Funds.


Tom Pearce

A small map of the mobility improvements project is located along 2.51 miles of northbound I-5 from Yesler Way to Lakeview Boulevard East in Seattle.