Courtesy of ACE

The Altamont Corridor Express (also known as Altamont Commuter Express or ACE) provides commuter rail service between Stockton and San Jose.  ACE uses diesel locomotive hauled Bombardier bi-level trains with 110 volt AC outlets, a bike car, and restrooms in every car.  ACE operates 4 round trips during weekday peak hours only (4 AM trips to San Jose, 4 PM trips to Stockton).

By the numbers

  • Route length: 85 miles
  • Daily ridership: ~ 2,500 passengers/day (2005)
  • Average passenger trip length: 48 miles (computed from NTD2004)
  • 10 rail stations in 3 counties: San Joaquin, Alameda, and Santa Clara.
  • 4 round trips on weekdays between Stockton and San Jose.

ACE projects

» ACEforward – various projects to increase track capacity between Stockton and San Jose

» ACE eastward extension from Lathrop t0 Modesto, Turlock, and Merced

» ACE northward extension from Stockton to Sacramento

» Rail connection between ACE and BART in the Tri-Valley

Governing body

ACE is managed by the San Joaquin Regional Rail Commission (SJRRC). They contract with Herzog Transit Services Inc. to operate the trains.


  • 1989: San Joaquin Council of Governments, Stockton Chamber of Commerce, and the Building Industry Association of the Delta begin developing a 20-year transportation plan. 1990: San Joaquin County Measure K half-cent sales tax for transportation passes.
  • 1995: County of San Joaquin forms a joint powers agreement that creates the San Joaquin Regional Rail Commission to implement the rail plan.
  • May 1997: Agreement between the San Joaquin Regional Rail Commission, Alameda Congestion Management Agency, and the Santa Clara Valley Transportation Authority to create the ACE Joint Powers Authority.
  • October 19, 1998: First day of ACE operations with 4 daily weekday trains — 2 westbound trains in the morning and 2 eastbound trains in the evening — operated by Herzog Transit Services, Inc. under contract with the San Joaquin Regional Rail Commission.
  • February 2000: ACE adds a morning turn-back train between San Jose and Fremont.
  • March 5, 2001: To alleviate overcrowding, ACE drops the turn-back train and adds a third round trip that departs Lathrop-Manteca later in the morning and returns in the evening, for a total of 3 westbound morning trains and 3 eastbound evening trains. It also begins stopping at the Santa Clara Caltrain station near downtown Santa Clara.
  • August 1, 2005: ACE suspends service at Santa Clara Caltrain station.
  • August 28, 2006: ACE adds a fourth round-trip between Stockton and San Jose, providing mid-day weekday service
  • November 2, 2009: ACE discontinues mid-day round-trip.
  • May 2012: ACE restores service at Santa Clara Caltrain station.
  • October 2012: ACE adds a fourth round-trip during peak hours.