I-405 Master Plan

What is the I-405 Master Plan?
Interstate 405 has long been one of the state’s most congested corridors. In 2002, after a three-year study of the area and extensive work with stakeholders up and down the corridor, WSDOT adopted an environmental impact statement for the corridor, which became the basis of the I-405 Master Plan.

The Master Plan is a set of long-term improvements we are working to achieve within the I-405 Corridor Program. The improvements are designed to get more people moving through the corridor with the completion of more than 150 individual but coordinated projects.

Is the Master Plan just highway improvements?
The plan includes all transportation modes, including new lanes in each direction, a corridor-wide bus rapid transit (BRT) line and bicycle and pedestrian paths. The plan aims to address bottlenecks such as the SR 167, SR 520, SR 522 and I-90 interchanges, improve key arterials, build new transit centers, and add about 1,700 new vanpools and over 5,000 park and ride spaces.

The I-405 Master Plan includes:

  • Up to two lanes on I-405 in each direction
  • A Bus Rapid Transit (BRT) line with stations along I-405 and expanded transit centers
  • Improvements to key arterials
  • 1700 new vanpools – a 100% increase
  • Increasing local transit service by 50% within the corridor
  • 5,000 new park-and-ride spaces
  • Eight new pedestrian/bicycle crossings over I-405
  • Potential managed lanes system

How are we doing so far?
For the last 15 years, we’ve focused on addressing the worst chokepoints first in Bellevue, Bothell, Kirkland and Renton. After several years of study, we also received Legislative direction to build express toll lanes between Bellevue and Lynnwood on I-405.

Here is an overview of our progress toward building Master Plan elements as of 2020:

  • Park and Ride expansions – 138% complete or funded
  • Transit center expansions – 70% complete
  • Bus Rapid Transit stations – 91% complete or funded
  • Local arterial improvements – 50% complete
  • Add 2 lanes in each direction – 55% complete or funded
  • Transit service increase – 62% complete or anticipated
  • Direct Access and Direct Connectors (system to system) – 35% complete or funded
  • Vanpool service increase – 40% complete
  • Pedestrian/bicycle improvements – 65% complete or funded
  • 50-mile Express Toll Lane System -- 95% complete or funded 

Some of our active projects within the I-405 Master Plan include: