Tri Delta Transit
| Parent | Eastern Contra Costa Transit Authority |
|---|---|
| Founded | 1977 |
| Headquarters | 801 Wilbur Ave, Antioch, California, United States |
| Locale | East Contra Costa County, California |
| Service type | bus service, paratransit |
| Routes | 17 weekday, 6 weekend |
| Stops | approximately 650 |
| Fleet |
|
| Daily ridership | 4,300 (weekdays, Q1 2025) |
| Annual ridership | 1,348,100 (2024) |
| Operator | Transdev |
| Website | trideltatransit.com |
Tri Delta Transit, formally the Eastern Contra Costa Transit Authority, is a joint powers agency (JPA) of the governments of Pittsburg, Antioch, Oakley, Brentwood, and Contra Costa County that provides bus service for the eastern area of Contra Costa County, California, United States. Contra Costa County has four major public bus transportation services, divided geographically: three mostly serve destinations within the county, covering western (WestCAT), central (County Connection), and eastern (Tri Delta Transit) regions, and one (AC Transit) serves Bayside cities along the western edges of Contra Costa and Alameda counties. In 2024, the system had a ridership of 1,348,100, or about 4,300 per weekday as of the first quarter of 2025.
Tri Delta Transit local buses connect to the BART rapid transit system at Antioch, Pittsburg Center, Pittsburg/Bay Point and Concord. In addition, Tri Delta Transit buses connect with Amtrak commuter rail services, including San Joaquins and Capitol Corridor. Within the county, several Tri Delta Transit bus routes connect with County Connection and WestCAT.