Watch: New Roundabouts, Overpass Coming To Gateway Of Napa County

NAPA VALLEY, CA — Caltrans and the Napa Valley Transportation Authority released a video Wednesday of the Highway 12/Highway 29 Soscol Junction Roundabout Project to demonstrate how it was designed to ease commuter times for motorists and improve access for pedestrians and bicyclists.

Construction started in June 2022 on the southern Napa project and is expected to continue until fall 2025; however, the intersection will open to traffic late this summer or early this fall. Soscol Junction sits at the base of Napa County and serves as a front door to one of the world's most iconic tourist destinations and winemaking regions.

The project replaces the signalized intersection of SR-12/29, SR-121 and Soscol Ferry Road with an interchange comprised of an overpass and two roundabouts—a configuration expected to significantly improve traffic flow, reduce congestion and enhance connectivity and safety for people who walk and bike, according to officials with Caltrans and the NVTA.

Unlike traditional intersections managed by traffic signals, they said, 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.

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

The project also added 1,200 feet of Class I bicycle lanes and walking paths, improving access for pedestrians and cyclists. Eventually, these lanes will connect to the Vine Trail, a 47-mile multi-use path from Calistoga to the ferry in Vallejo.

"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.

The project cost $54 million and was funded with $19.7 million from Senate Bill 1—the Road Repair and Accountability Act of 2017 — along with $29.8 million in state and regional funds and $3.7 million in local funds.

Low-Profile Project Meets Traffic Needs

Napa Valley is one of the most visited destinations in California, with nearly five million visitors annually. With the proliferation of wineries, resorts and restaurants, the number of employees commuting into the valley from other parts of the Bay Area was also destined to increase.

In addition to tourist traffic and commuters, freight traffic was once consigned to transporting agricultural products and equipment but has dramatically increased with the rise of the hospitality industry in Napa Valley.

If it weren't enough that three roads —SR-12/SR-29, State Route 221 and Soscol Ferry Road — met at one intersection, nearby Devlin Road also funnels traffic onto Soscol Ferry Road not far from the junction.

To reduce the traffic congestion created at this confluence, a flyover was constructed to connect southbound SR-29 to southbound SR-221 and northbound SR-221 to northbound SR-29. Beneath the flyover, two roundabouts distribute traffic to the remaining interconnections.

According to Caltrans, local leaders, residents and business owners strongly opposed a monolithic structure and favored a less obtrusive interchange conducive to Napa Valley's natural beauty.

The Soscol Junction Project was designed to move traffic while keeping a low profile. Additionally, the interchange supports multi-model traffic, with a Class -1 pedestrian and bicycle path encouraging other means of travel.

In July 2022, the project was delayed by about a week when birds — Swainson Hawks — nested on the property to house their fledgling young.