I-5 – Mounts Road to Steilacoom-DuPont Road Corridor Improvements

Background

The Washington State Department of Transportation is in the third phase of a series of projects that widen Interstate 5 from Mounts Road near DuPont to Gravelly Lake Drive in Lakewood. Southbound I-5 previously narrowed from four lanes to three, just past 41st Division Drive. This project extended the existing southbound I-5 high occupancy vehicle lane to Steilacoom-DuPont Road. The new northbound HOV lane now extends from Mounts Road to the existing HOV lane at 41st Division Drive. The new HOV lanes opened in June 2026.

At the Steilacoom-DuPont Road interchange (exit 119), a new overpass was completed and opened to traffic in early 2026. The new overpass creates enough space to extend the I-5 HOV lanes further south into DuPont and provides increased vertical clearance over the interstate to meet current standards.

The aerial shows where southbound I-5 narrows down from four lanes to three, just past 41st Division Drive.

Traffic flow was constrained by the proximity of the I-5 ramp intersections, Joint Base Lewis-McChord’s DuPont Gate, the railroad, and the intersection of Wilmington Drive and Barksdale Avenue. The new Steilacoom-DuPont Road interchange provides increased distance between the intersections while maintaining access to neighboring communities and JBLM. The old overpass was removed in April 2026.

Design changes and benefits

Improvements include an extended HOV lane in both directions of I-5. Crews will build a partial diverging diamond interchange at the new Steilacoom-DuPont overpass and a roundabout. There also will be improved access to and from JBLM.

This project features a number of design changes around the Steilacoom-DuPont Road interchange to improve access and reduce traffic congestion. The changes and benefits include:

• Extending the HOV lanes in both directions of I-5. The northbound HOV lane now starts at Mounts Road. The southbound HOV lane was extended from 41st Division Drive south into DuPont.
  • Increases capacity in this section of I-5 and reduces chronic traffic congestion.

• A new Steilacoom-DuPont Road overpass and a partial Diverging Diamond Interchange (DDI).
  • The new overpass crosses over the railroad, eliminating an at-grade crossing. The DDI reduces vehicle conflict points and improves efficiency with fewer traffic signals.
• Barrier-separated shared-use path on the new Steilacoom-DuPont Road overpass spanning I-5.
  • Improves pedestrian access by connecting JBLM to communities west of I-5 for people who walk, bike, or roll.

• Roundabout connecting the new overpass and Steilacoom-Dupont Road.
  • Improves efficiency for all users on the west side of I-5.
• Dedicated lanes at the reconstructed interchange that separate traffic traveling to either the JBLM DuPont Gate or the communities on the west side of I-5.
  • Improves efficiency through the interchange.

Construction

Keeping you moving throughout construction

The new Steilacoom-DuPont interchange is in its final configuration. All construction is expected to be complete in August.

June-August 2026: HOV lanes open and project wraps up

The new HOV lanes opened through the project area in June. Additionally, crews finished work on the Steilacoom-DuPont Road on-ramp to southbound I-5. This includes adding guardrail, lighting, new pavement and lane markings up to the Center Drive off-ramp.

How to get around

The new overpass is a diverging diamond interchange, similar to the one on Marvin Road in Lacey. Driving through a diverging diamond is as easy as following the signs and lane lines.

To learn more about how to navigate a diverging diamond interchange, watch the video below and review WSDOT’s online resources.

Changes to Wilmington Drive and Barksdale Avenue intersection

With the closure and removal of the former Steilacoom-DuPont Road overpass, there is a new three-way intersection north of the old railroad crossing. Traffic lights have been removed and replaced by three new stop signs at the Wilmington Drive and Barksdale Avenue intersection. Additional changes include:

• A new sidewalk that connects Wilmington Drive to Steilacoom-DuPont Road for people walking or rolling to or from Barksdale Station.
• The addition of a left turn lane into Barksdale Station, and the removal of the existing concrete median curb.
• Dedicated left turn lanes to and from the Historic Village.

Design visualization of how this intersection will look when construction is complete.

What's next

This project is anticipated to be complete in August 2026. The final phase of work includes drainage work, landscaping and striping. No additional lane or ramp closures are expected beyond August.

Please help keep road workers safe. When approaching a work zone, remember to:

• Slow down – drive the posted speeds for worker and traveler safety.
• Be kind – workers are out there helping to keep people safe and improve the roadways.
• Pay attention – both to workers directing travelers and surrounding traffic.
• Stay calm – expect delays, leave early or take alternate routes if possible; no meeting or appointment is worth risking someone’s life.

Stay connected

Travel conditions change quickly, we strongly encourage travelers to use the tools below to stay informed.

• View updates and upcoming closures on the project webpage
• Check real time travel conditions, view cameras and travel times
• Download WSDOT’s free smartphone app
• Sign up for email updates using GovDelivery