SR37/Fairgrounds Dr Interchange, Vallejo: STA & Caltrans Begin Next Phase of Construction

April 3, 2026

Date: 2 April 2026
Agency: Solano Transportation Authority, Caltrans District 4-Bay Area
Contact:  Sean Person, Sabrina Martinez
Phone: (707) 399-3217, Phone: (510) 934-5257

State Route 37 (SR 37)/Fairgrounds Drive Interchange in Vallejo: Solano Transportation Authority and Caltrans Begin the Next Phase of Construction

SOLANO COUNTY  – The Solano Transportation Authority (STA), in close coordination with its transportation partner, the California Department of Transportation (Caltrans), is continuing construction work on the new State Route 37 (SR 37)/Fairgrounds Drive Interchange Project in Vallejo. The interchange improvement project will enhance motorist safety and improve bicycle and pedestrian access with construction of a new Diverging Diamond Interchange. This is the first-ever Diverging Diamond Interchange (DDI) constructed in the Bay Area and only the second-ever constructed on a major highway in California.

Coming Soon!
Thank you for your continued cooperation during construction of the new State Route 37/Fairgrounds Interchange. Construction is nearing completion and the new Diverging Diamond Interchange is expected to open to traffic in the early summer, weather permitting.

The Diverging Diamond Interchange will provide a safer, easier entrance to Vallejo while improving accessibility for residents and businesses near the SR 37 and Fairgrounds Drive corridor. The new interchange will improve traffic flow in the area, increasing connectivity to regional transit, the greater Vallejo area, and employment and recreation centers, including Six Flags/Discovery Kingdom. The project will allow bicyclists and pedestrians a more direct bike path to Vallejo from surrounding communities, such as American Canyon and Napa, and low-cost transportation options to local attractions.

Please visit the STA website for more information. Navigating the Diverging Diamond is easy! Just follow the road! Please watch the informational video available on the STA website for more information.

What to Expect Prior to the Opening of the new Diverging Diamond Interchange:
In early April, traffic on Fairgrounds Drive will be shifted in the northbound and southbound directions under SR 37 to allow for the new median to be constructed.

The following construction impacts may be expected in early April 2026:

• Motorists on Fairgrounds Drive at SR 37 should watch for temporary traffic lane shifts and follow all on-site signage. The eastbound off-ramp at SR 37/Fairgrounds Drive will be closed overnight with detours. Closures are scheduled from 10:00 PM until 6:00 AM.
• The westbound on-ramp from Fairgrounds Drive to SR 37 will be closed overnight with detours. Closures are scheduled from 8:00 PM until 6:00 AM.

Motorists should drive with caution in construction zones and expect travel delays. All work is weather dependent.

We appreciate the community’s and motorists’ cooperation and patience as important work to improve the safety and accessibility of this important project continues!

To learn about how to use the DDI, please watch our informational YouTube video at https://youtu.be/L7QOoovsVuU?si=AOsSTF2hREcpQwhA.

For general questions, please email our project team at: SR37-FairgroundsPIO@portal3.pbid.com.

For more information about the project and to view a video explaining the DDI design, please visit https://sta.ca.gov/project/redwood-parkway-fairgrounds-dr-improvementproject/.

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