About Us

Our Origins

During the 1980s, three fast-growing regions in California - Silicon Valley, Tri-Valley, and San Joaquin Valley - faced inadequate public transit connections, resulting in increased congestion on Interstate 580 and Interstate 680. To commute between the San Joaquin Valley or Tri-Valley and Silicon Valley, people had to rely on personal vehicles or scarce bus services.

In 1995, the San Joaquin Regional Rail Commission (SJRRC) was established by San Joaquin County and seven cities along the intended route to oversee the development of the service. In May 1997, the Altamont Commuter Express Joint Powers Authority (ACE JPA) was created through a collaboration between the SJRRC, Santa Clara Valley Transportation Authority (VTA), and Alameda Congestion Management Agency (ACMA). This partnership set the foundation for financial backing, administrative procedures, and governance of the rail service. Funding for the operation primarily comes from state and federal sources, predominantly sales tax revenue collected by the three JPA signatories. Farebox revenues contribute to approximately one-third of the costs.

The original Altamont Commuter Express (ACE) service used two trainsets with a seating capacity of 1,120 passengers per direction daily. After quickly reaching near-full capacity, the service underwent several expansions and improvements. However, due to the dot-com recession and the Great Recession, ACE experienced ridership fluctuations and faced funding challenges, leading to temporary service suspensions and cutbacks. Over the years, ACE has added more round trips and restored service to certain stations, adjusting to ridership demands and available funding.

In December 2012, the service was rebranded from Altamont Commuter Express to Altamont Corridor Express to reflect a broader scope of service. In March 2014, ACE opened a $65 million maintenance facility in Stockton.

In conjunction with the California High-Speed Rail project, plans were made to significantly upgrade and expand the ACE line. Initial plans aimed for a high-speed rail "Super ACE," but these were later replaced with the more modest ACEforward program. The San Joaquin Regional Rail Commission issued a notice of intent for an Environmental Impact Statement in June 2013, released in 2017, outlining short-term and long-term goals. Short-term goals include track improvements, potential rerouting, new stations, and an extension to Modesto. Long-term goals include upgrading the existing corridor to allow up to 10 daily round trips, extending the service to Merced, and electrifying the line from Stockton to San Jose.


Funding Partners

Alameda County

The Alameda County Transportation Commission (Alameda CTC) supports the Alameda County portion of ACE service operations using Measure B funds. Measure B, a half-cent sales tax, was approved by Alameda County voters in November 2000. ACE Service is allocated 2.12% of Measure B's net revenues for its operations. The ACTC's contribution from Measure B is set to conclude in 2022.

San Joaquin County

The San Joaquin Council of Governments (SJCOG) manages the Measure K Program, which is a half-cent sales tax designated for transportation projects in San Joaquin County. As the Local Transportation Authority, SJCOG is in charge of distributing sales tax revenue to various local transportation initiatives.

Santa Clara County

Measure A Transit Improvement Program, a voter-approved half-cent sales tax in Santa Clara County, collects revenue to be utilized for both capital enhancements and operational expenses within the county's transportation sector.


SB-1, SB-132, TIRCP, TDA, LCTOP, PROP 1A and PROP 1B are state initiatives that provide funding to ACE.


Urbanized Area Formula Program (5307), State of Good Repair Program (5337), Congestion Mitigation and Air Quality (CMAQ), Capital Investment Grant Program (5309) are federal initiatives that fund the ACE.

Transit Partners


ACE and the Environment

ACE has always been environmentally focused since its inception. 

Our maintenance facility is state-of-the-art and has incorporated a variety of sustainable features such as 1,100 solar photovoltaic panels that provide 20% of the building's total power consumption, daylight harvesting systems to reduce the dependency on electric lighting for adequate illumination, electrocoagulation equipment for separating oils and water to enable proper sewer discharge, specialized window shades that track the sun, and a 102,000-gallon rain harvest tank as an integral component of the reclaimed and reused water system.

We are conducting emissions and fuel consumption tests to obtain data on the advantages, such as reduced emissions and cleaner combustion, compared to the cost factor of the biodiesel product utilized in the ACE fleet.

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