I-5 - Tumwater to Mounts Road Corridor Study

I-5 Tumwater to Mounts Road Study Area Map

Study News

Study staff have completed a summary of results (pdf 356 kb) from the two surveys the agency conducted to support the study process. WSDOT received and reviewed a total of about 4,600 responses to the surveys in total which included roughly 6,500 open-ended responses.

WSDOT and study partners like Thurston Regional Planning Council (TRPC), used this input to refine and adjust study goals and priorities. For example, the study team added the study goal of resilience to disruption as a result of the surveys.

WSDOT and TRPC are currently working to model various types of strategies and solutions that could address performance issues and support study goals in the future. The results of this work will inform the recommendations of the study and will be detailed in the final report.

I-5 Tumwater to Mounts Road Survey Summary (pdf 355 kb)

Study Purpose

WSDOT is studying transportation system performance on I-5 through Tumwater, Olympia and Lacey in collaboration with local partners. The study area extends from the SR 121/93rd Avenue SE/Tilley Road Interchange in Tumwater to Mounts Road just east of the Nisqually River. This segment of highway travels through Tumwater, Olympia and Lacey and is a major freight and commuter corridor. This section of I-5 experiences congestion, recurring delay, and unreliable travel times. Multiple factors contribute to these issues such as traffic volumes and merging at interchanges. WSDOT's goal is to recommend a set of performance-based strategies to achieve the following outcomes in the study area over the next 20 years:

  • Improve travel times and make them more predictable
  • Increase the ability of I-5 to efficiently and equitably move people and goods
  • Improve access to industrial and commercial areas and job sites
  • Protect and enhance the environment including reducing the transportation-related impact on wildlife habitat in the Nisqually River delta
  • Improve the transportation system's ability to operate during and recover from disruptions such as traffic incidents

The End Result

WSDOT will publish a report at the end of the study that will recommend strategies to improve system performance and manage congestion in the study area. These recommendations will be based on data and analysis from the study and local community input.


Fall 2018

  • Local government and community engagement
  • Data collection and analysis, develop improvement strategies

Winter 2018

  • Continued local government and community engagement
  • Refine and finalize improvement strategies

Spring - Summer 2019

  • Model improvement strategies and evaluate results
  • Draft initial study report

Fall - Winter 2019

  • Online and in-person public meetings to review and comment on recommended strategies
  • Publish final report


The study is funded through state and local appropriations totaling $550,000.


Dennis Engel, Multimodal Planning Manager

Karen Parkhurst, TRPC Programs & Policy Director

Bradley Bobbitt, Study Staff