Date: November 24, 2025
Agency: Solano Transportation Authority, Caltrans District 4-Bay Area
Contact: Contact: Sean Person, Geoffrey Johnson
Phone: (707) 399-3217, (510) 421-7348
State Route 37/SR-37- Fairgrounds Drive Interchange- Vallejo
Construction Shifts into Gear- December 2025
Watch for Traffic Lane Shifts/Overnight Ramp Closures
SOLANO COUNTY – The Solano Transportation Authority (STA), in close coordination with its transportation partner, the California Department of Transportation (Caltrans), has started 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 divergent diamond interchange. This is the first-ever divergent diamond interchange (DDI) constructed in the Bay Area and only the second-ever constructed on a major highway in California.
What to Expect During Initial Construction Work
Construction at SR 37 and Fairgrounds Drive started construction in April 2025. The site is near the Six Flags Discovery Kingdom Theme Park and the Solano County Fairgrounds. In May traffic in both directions was shifted to the west side of SR 37 and a temporary pedestrian walkway was constructed. Beginning mid-December, traffic will be shifted to the east side of SR 37, under the freeway.
Weather permitting, the following construction-related activities are scheduled to happen in mid-December, 2025.
- 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 eastbound on-ramp from Fairgrounds Drive to SR 37 will be closed nightly from 10:00 PM – 5:00 AM.
- The westbound off ramp from SR 37 to Fairgrounds Drive will be closed nightly from 11:00 PM – 5:00 AM.
- The westbound on-ramp from Fairgrounds Drive to SR 37 will be closed nightly from 8:00 PM – 6:00 AM.
Motorists should drive with caution in construction zones and expect travel delays. All work is weather dependent.
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-improvement-project/.
STA and Caltrans thank the motoring public for its patience and understanding as we work to improve and maintain our state’s highways.






