Soscol Junction Interchange Project-Napa County

New interchange relieves congestion at the junction of State Route 29, State Route 221 and Soscol Ferry Road

Napa Valley Transportation Authority (NVTA) and Caltrans completed the Soscol Junction Interchange Project, a three-year $56.7 million project to reduce congestion and improve traffic operations in southern Napa County.

To reduce the traffic congestion created by this confluence of routes, Caltrans built a grade-separated interchange with an overpass connecting southbound SR 29 to southbound SR 221 and northbound SR 221 to northbound SR 29, allowing for free-flowing traffic.  Beneath the overpass, Caltrans constructed two roundabouts to distribute traffic to the connecting surface streets.

The Soscol Junction Interchange Project was designed to move traffic, while keeping a low profile.  Additionally, the interchange supports multi-model traffic, Class-1 pedestrian and bicycle path, as alternative means of travel is another goal of the project.

The project included 1,200 feet of Class-1 facility to accommodate bicycles/pedestrians through the intersection.

• Start Construction: Summer 2022
• Open for Traffic: Fall 2024
• Finish Construction: Fall 2025

UPDATE: June 2025

Soscol Junction nominated for state interchange award! 

Built in partnership with Caltrans District 4 and the Napa Valley Transportation Authority (NVTA), Napa County’s Soscol Junction Interchange project was honored as a top three finalist in the Interchange Project category at the 36th annual California Transportation Foundation (CTF) Transportation Awards on June 12. Although Soscol Junction did not win, this prestigious recognition celebrates excellence and innovation in transportation projects across the state.

“The Soscol Junction Interchange addresses one of Napa County’s most critical and persistent traffic bottlenecks. By replacing the signalized intersection at State Routes 29/221 and Soscol Ferry Road with two roundabouts and an overpass, the project significantly improves safety and reduces congestion for commuters, residents and visitors,” said Caltrans District Director Dina El-Tawansy.

The Soscol Junction Interchange addresses one of Napa County’s most critical and persistent traffic bottlenecks. By replacing the signalized intersection at State Routes 29/221 and Soscol Ferry Road with two roundabouts and an overpass, the project significantly improves safety and reduces congestion for commuters, residents, and visitors.

“This recognition is especially meaningful — our team has poured more than a decade of dedication into making the Soscol Junction a reality,” said Kate Miller, NVTA Executive Director.

This new infrastructure will save 1.35 million hours of vehicle delay a year, reducing carbon emissions by 94,000 tons over the next 20 years. That’s the equivalent of removing 22,372 cars from our roads for one year. The addition of a pedestrian and bicycle facility increases access for all road users. Construction on the $56 million project began in the summer of 2022, and Soscol Junction opened to traffic in the summer of 2024.

The new Highway 101/De La Cruz/Trimble Roadd project in San Jose, sponsored by VTA, was named Interchange Project winner at the CTF’s annual awards ceremony in Irvine, Calif., on June 12, 2025. Still, both agencies are honored to be recognized as one of the most impactful transportation projects in California.

UPDATE: September 2024

The near completion of the Soscol Junctrion Interchange project was cause for celebration on Sept. 13, 2024, as NVTA and Caltrans hosted a ribbon cutting event. As the project was already open to traffic, Meritage Resort and Spa generously provided the venue for the day, which was sponsored by GHD and Ghilotti Construction. Speakers included NVTA Executive Director Kate Miller, Napa County Supervisor Ryan Gregory, NVTA Board Chair Mark Joseph, Caltrans Bay Area District Director Dina El-Tawansy, Rep. Mike Thompson and Sen. Bill Dodd.

While the major elements of the project are completed, there will be additional plantings and other maintenance to put the final touches on Soscol Junction. See more photos of the Ribbon Cutting Ceremony with Rep. Mike Thompson and Sen. Bill Dodd. 

UPDATE: Summer 2024

The Napa Valley Transportation Authority (NVTA) and Caltrans released a video demonstrating how the State Route 12/29/221 Soscol Junction Roundabout Project will ease commuter times for motorists and improve access for pedestrians and bicyclists.

The funding for the $54 million southern Napa project includes nearly $20 million from Senate Bill (SB) 1, the Road Repair and Accountability Act of 2017, and is expected to be completed in fall 2024.

The three-year project replaces the signalized intersection of State Route 12/29, State Route 221, and Soscol Ferry Road with an interchange composed of an overpass and two roundabouts—a configuration that will significantly improve traffic flow, reduce congestion, and enhance connectivity and safety for people who walk and bike.

Unlike traditional intersections managed by traffic signals, roundabouts compel motorists to slow down in all directions and proceed with caution—creating more opportunities to spot other vehicles and see bicyclists and pedestrians who also share the roadway.

“Working with the Napa Valley Transportation Authority, we created a plan to construct an interchange that significantly improves safety, reduces traffic congestion, and also blends compatibly with the surrounding ecology,” said Sean Nozzari, Caltrans Bay Area Deputy Director of Traffic Operations.

In addition to the $19.7 million in SB1 funding, the project is supported with $29.8 million in state and regional funds, and $3.7 million in local funds.

Sitting at the base of Napa County, Soscol Junction serves as a front door to one of the most iconic tourist destinations and winemaking regions on the globe.

“The Soscol Junction Project will dramatically improve travel near the gateway to downtown Napa, and other parts of this remarkable Valley,” said Liz Alessio, Chair of the Napa Valley Transportation Authority.

The project also improves access for pedestrians and cyclists with1,200 feet of Class I bicycle lanes and walking paths. Eventually these lanes will connect to the Vine Trail, a 47-mile multi-use path that will stretch from Calistoga to the ferry in Vallejo.

For more information, visit the Soscol Junction Project webpage.

UPDATE: March 2023

Napa County attracts more than five million visitors annually. Coupled with population growth in Solano and Sonoma Counties, Highways 29 and 221 have become major interregional highways serving residents, visitors, workers, and freight.

Annually commuters endure up to 225* hours of delay in the morning and 630* hours of delay in the evening at Soscol Junction due to congestion. The Soscol Junction project is a crucial step in relieving future traffic congestion.

Congestion at Soscol Junction has worsened over time, fueled in part by tourism, population growth and economic development. Housing production is not keeping pace with the creation of new jobs in Napa. Consequently, Napa’s workers commute in from adjacent counties contributing to the traffic issues.

The existing highway configuration cannot accommodate the current traffic volumes – volumes that are likely to grow in the future.

Looking for some fast facts?
Click here to view the fact sheet.

What’s the new Soscol Junction going to look like?
Watch the video and find out!

UPDATE: Jan. 11, 2024

After a brief one-lane closure last weekend, a new overpass is now open for northbound traffic at the intersection of State Route 29, State Route 221 and Soscol Ferry Road — part of an expansive effort to relieve congestion in southern Napa.

Drivers continuing onto northbound SR 29 from southbound SR 221 will notice a new exit ramp from SR 221 prior to the signalized intersection connecting drivers directly to northbound SR 29. In addition, drivers traveling southbound on SR 221 are no longer able to make a right turn at the signalized intersection to northbound SR 29 and must instead use the new exit ramp from SR 221.. These infrastructure enhancements are part of the $54 million Soscol Junction Project that is slated for completion this fall.

The multiyear construction project will replace the signalized intersection with an interchange composed of an overpass and two roundabouts. The new configuration will add fluidity to traffic flows, reduce congestion and enhance connectivity.

Annually, commuters endure up to 225 hours of delay in the morning and 630 hours of delay in the evening at the clogged Soscol Junction. In response, the Napa Valley Transportation Authority and Caltrans teamed up to bring relief to the busy intersection.

The project will also include a new 1,200-foot Class I bicycle and pedestrian path. Eventually the path will connect to the Vine Trail, a 47-mile multi-use path that will stretch from Calistoga to the Vallejo ferry.

In addition to funding from the Road Repair and Accountability Act of 2017 (SB-1), the Soscol Junction Project will be paid for with $29.8 million in state and regional funds and $3.7 million in local funds.

UPDATE 12/29/23

TRAVEL ADVISORY- Northbound State Route 29 Weekend Single Lane Closure From NB SR29/S221 Intersection to Napa Valley Corporate Drive

For Paving and New Alignment of Northbound Lanes on State Route 29 in Napa County.

The Northbound State Route 29 weekend single lane closure is scheduled to begin at 7:00 p.m. Saturday, January 6 and will be in place until 5:00 a.m. Monday, January 8.

One lane on Northbound State Route 29 will remain open.

NAPA COUNTY- Caltrans has scheduled single lane closures on Northbound State Route 29 between NB SR29/SR221 to Napa Valley Drive. Crews will be working on a paving operation and a new alignment of new roadway grade part of the Soscol Junction project. To ensure the safety of workers and motorists, single lane reductions will be in place on SR-29. One Lane will be always open to traffic on each direction.

Crews will begin work beginning Saturday night January 6, 2024.

All work is weather dependent.

Alternative scheduled dates are the weekend of January 20th, or January 27th, 2024.
Please drive with caution. Slow for the Cone Zone and Be Work Zone Alert.
For real-time information, please visit Caltrans QuickMap

UPDATE 6/22/22

We’ve broken ground on the Soscol Junction project! Click here to read the press release.

UPDATE 12/3/2020
The Soscol Junction project is fully funded! Click here to read the press release.

UPDATE 2/10/2020
Caltrans Adopted the Final Environmental Document for the Soscol Junction Project. You can view is using the link on the right.

UPDATE 10/11/19 (Click on lower right-hand corner of image frame to view in fullscreen mode.)
Caltrans delivered a presentation on Soscol Junction, along with simulated views and studies on traffic and transportation. Click on the picture below to download the PowerPoint slide deck:

UPDATE 9/20/19
Caltrans released an environmental document for the Soscol Junction Improvement Project in Napa County. The Project proposes improvements to the existing State Route 29 / State Route 221 signalized intersection. The environmental document is an Initial Study with Proposed Mitigated Negative Declaration/Environmental Assessment under both CEQA and NEPA. A public meeting was held at NVTA offices (625 Burnell Street Napa, CA 94559) on Tuesday, October 8, 2019 from 5:30pm to 7:30pm. Comments on the document were accepted through October 20, 2019.