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.[1] 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 third quarter of 2025.
The Eastern Contra Costa Transit Authority (ECCTA) JPA was formed in 1976 by the cities of Antioch, Brentwood, and Pittsburg, along with the County of Contra Costa. When Oakley was incorporated in 1999, the JPA was amended to admit Oakley on April 1, 2001.[4]:1 The Tri Delta Transit name was selected in May 1977 by the marketing committee of the ECCTA.[5]
Tri Delta Transit fixed route service began on June 6, 1977, celebrated by an inaugural bus starting from Antioch City Hall (10a.m.), traveling to Oakley (10:30), Brentwood City Hall (11), Pittsburg, and ending in West Pittsburg (2p.m.). For the first week, free rides were offered.[6] Initial service was provided for two local routes in Antioch and Pittsburg, which connected with express bus service serving BART.
AC Transit operated the service under contract until 1984, when it was transferred to a private operator,[4]:1 and ECCTA acquired its first buses; prior to that, AC Transit owned the buses it used for Tri Delta Transit.[7] Some of the buses used in 1978 included 29-foot models, shortened from 35-foot buses at the AC Transit shops.[8]
Dial-a-ride on-demand transit services have been provided since 1979 using contracted private operators. ECCTA consolidated fixed route and on-demand services with a single operator when the contract with AC Transit was discontinued in 1984.[7] In 1986, Laidlaw Transit, Inc. (later First Transit, now Transdev) begin operating Tri Delta Transit.[7]
The ECCTA headquarters in Antioch was built in 1987, consolidating administration, operations, and maintenance at a single facility; expansions in 2004 provided additional space and bus parking.[4]:1
Tri Delta Transit operates in eastern Contra Costa County and has stops in Antioch, Oakley, Brentwood, Bay Point, Pittsburg, Martinez, and Concord. Tri Delta Transit operates local and express routes on weekdays and local routes on weekends and holidays.
Transfers
Intra-system transfer points for the majority of Tri Delta Transit's routes include:
In addition to transfers within Tri Delta Transit and to BART, riders may transfer to neighboring and long-distance public transportation systems at other stations, including:
Tri Delta Transit operates thirteen bus routes on weekdays, serving the cities of Bay Point, Pittsburg, Antioch, Oakley, and Brentwood, with one route each connecting to Concord (201X) and Martinez (200X). Most routes parallel the San Joaquin River, running east and west; routes designated as "express" (200X, 201X) are designed with fewer stops and operate primarily during commute hours with limited mid-day service. Several routes share the same terminal points, but take different paths to provide service to communities both north and south of California State Route 4.[9] For example, 370 and 371 both provide service between the Pittsburg/Bay Point and Antioch BART stations.
On the weekends and holidays, Tri Delta Transit operates eight of the thirteen routes throughout the ECCTA service area including the aforementioned cities with the exceptions of Concord and Martinez. Routes numbered 37x operate all week long, with reduced service frequencies on weekends and holidays.[10]
↑Subset of legacy route 380, truncated at Los Medanos College (western terminus) and Antioch High School (eastern terminus). Limited service, with one trip each in the mornings and afternoons.[13]
↑Adopts aspects of legacy routes 388 & 390 west of Railroad Ave (Pittsburg), 387 & 390 between Railroad and Loveridge, 380 & 387 between Loveridge and Somersville, 387 between Somersville and G, and 380, 388, and 387 east of G. Runs on Leland west of Somersville, then Sycamore and 18th east of Somersville.[17]
↑Adopts aspects of legacy routes 380 west of Railroad Ave (Pittsburg) and 388 east of Loveridge. Generally serves neighborhoods north of SR 4.[19]
↑Largely replicates legacy route 387, with eastern terminus moved to Los Medanos College. Serves neighborhoods within Pittsburg.[21]
↑Operates loop service in Pittsburg via Buchanan and Harbor
1234Operates exclusively on weekends and holidays, no weekday service[35]
↑"Early Bird Express" operated as a westbound-only route by Tri Delta Transit before regular weekday eBART service starts at 5a.m.;[54] eliminated starting from June 10, 2024.[55]
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