I-90 Two Way Transit and HOV Operations Stage 3

Sound Transit

Seattle, Washington
Estimated Cost:
$185 million
Constructability Review
Market Sector:
Facility Specialty:
Highways, streets, parking lots



The I-90 Two Way Transit and HOV Operations Stage 3 began construction after the completion of the first two phases that worked on the Eastbound and Westbound HOV lanes from Bellevue Way to 80th Ave SE. Phase 3 focused on the rest of the HOV lanes from 80th Ave SE to Ranier Ave.


Phase 3 required:


  • Structural interdisciplinary coordination between teams

  • Balancing

  • Testing

  • Risk assessments

  • Commissioning of ventilation

  • Fire suppression


  • ITS systems - in order to maintain properly balanced existing systems until the transitional and new systems are phased in. 

The focus of the constructability review was on the HOV lane to and from Seattle to improve the tunnel fire/life safety systems, improve Mount Baker Ridge and Mercer Island tunnels, bike path screening, as well as adjustments to accomidate for the East Link Light Rail project.

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