Greenroads Certified Bronze

23rd Ave Corridor Improvements Phase 1



Engineers Estimate: $31 million

Construction Value: $27.3 million 

Length: 2.9 lane-miles 

Owner: City of Seattle

Primary Design: Perteet, Inc. 

Design Support: HNTB 

Contractor: Gary Merlino Construction Company 

Functional Class: Arterial

Greenroads Version: v1.5  


The 23rd Ave Corridor Improvements Project is a three-phase reconstruction of a critical arterial in the Central District and adjacent neighborhoods of Seattle, WA. The existing roadway consisted of four narrow lanes over much of the corridor contributing to frequent collisions and delays from left turns. The improvement Project consists of replacing the existing failing pavement and restriping to create a single lane in each direction with a center turn lane. The conversion is accompanied by upgraded utilities, new sidewalks, extensive landscaping, upgraded lighting, and bus pullouts and new stop amenities, resulting in a safer roadway accessible to all users.


Sustainable features of the Project focus on increasing multimodal access along the corridor while improving safety. A number of responsible design and construction practices were implemented to reduce environmental impacts as well as lifecycle costs. Project highlights include:

  • 40-year pavement design life used for primary travel lanes 
  • Reconstruction of narrow, aging sidewalks
  • Restriping of travel lanes to increase lane width, reduce collisions and backups
  • Bus pullouts and upgraded stops with real-time arrival info
  • Intelligent transportation systems such as transit and emergency vehicle signal priority, wireless sensor detection, pedestrian safety signs, and CCTV cameras
  • Extensive revegetation using adapted species with limited irrigation requirements 
  • Prominent art installation incorporating site specific themes


23rd Phase 1 - Center Turn Lane

23rd Phase 1 - Paving

23rd Phase 1 - Intersection Improvements

23rd Phase 1 - Construction