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Altamont Corridor Express
Commuter rail service in Northern California
Commuter rail service in Northern California
| Field | Value | |
|---|---|---|
| name | Altamont Corridor Express | |
| image | Altamont Corridor Express logo.svg | |
| imagesize | 200px | |
| image2 | ACE Altamont Pass.jpg | |
| imagesize2 | 300px | |
| caption2 | ACE train climbing its namesake Altamont Pass in 2010 | |
| owner | San Joaquin Regional Rail Commission | |
| area served | San Joaquin Valley, Tri-Valley and Silicon Valley | |
| transit_type | Commuter rail | |
| stations | 10 | |
| daily_ridership | () | |
| annual_ridership | () | |
| headquarters | Robert J. Cabral Station in Stockton, California | |
| website | ||
| began_operation | ||
| operator | Herzog Transit Services | |
| marks | ACEX | |
| host | ||
| vehicles | 10 locomotives, 30 passenger cars | |
| train_length | 1–2 locomotives, 4–8 passenger cars | |
| system_length | 85 mi | |
| track_gauge | ||
| average_speed | 39 mph | |
| top_speed | 79 mph | |
| map | {{switcher | |
| {{maplink-road | from | Altamont Corridor Express.map}} Altamont Corridor Express highlighted in purple |
| {{Altamont Corridor Express | inline | yes}} |
| Altamont Corridor Express highlighted in purple |Show interactive map | |Show route diagram
The Altamont Corridor Express (ACE) is a commuter rail service in California, connecting Stockton and San Jose during peak hours only. ACE is named for the Altamont Pass, through which it runs. Service is managed by the San Joaquin Regional Rail Commission, and operations are contracted to Herzog Transit Services. The 86 mi route includes ten stops, with travel time about 2 hours and 12 minutes end-to-end. In , the line had a ridership of , or about per weekday as of . ACE uses Bombardier BiLevel Coaches, MPI F40PH-3C locomotives, and Siemens Charger locomotives.
Altamont Commuter Express began on October 19, 1998, with two weekday round trips. A third round trip was added in May 2001, followed by a fourth round trip in October 2012. The service was rebranded as Altamont Corridor Express in 2012. Saturday service began in September 2019, but was suspended in March 2020 due to the outbreak of COVID-19. The tracks are owned by Union Pacific Railroad, previously built along the Western Pacific Railroad main line. Under the ACEforward program, a number of improvements to the service are being considered. These include a rerouted line through Tracy, an extension to Modesto and Merced, and connections to BART at Union City and Tri-Valley.
History and funding
Planning
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By the 1980s, three rapidly growing areas in California – Silicon Valley, the Tri-Valley, and the San Joaquin Valley – were poorly connected by public transit, as Interstate 580 and Interstate 680 became more congested. Commuting from the San Joaquin Valley or the Tri-Valley to Silicon Valley required using a car or limited bus service.
In 1989, the San Joaquin Council of Governments, Stockton Chamber of Commerce, and the Building Industry Association of the Delta started work on a 20-year transportation plan for the northern section of the San Joaquin Valley. In November 1990, San Joaquin County voters passed Measure K, a half-cent sales tax to fund a variety of transportation improvements. The highest-priority project was the establishment of passenger rail service to San Jose.
In 1995, San Joaquin County and seven cities along the route formed the San Joaquin Regional Rail Commission (SJRRC) to oversee the creation of the service. In May 1997, the Altamont Commuter Express Joint Powers Authority (ACE JPA) was formed by the SJRRC, Santa Clara Valley Transportation Authority (VTA), and Alameda Congestion Management Agency (ACMA). That agreement formalized financial support, administrative processes, and governance for the rail service. The operation is funded by a variety of state and federal sources, largely sales tax revenue collected by the three JPA signatories, while farebox revenues account for about one-third of costs.
Cost sharing for capital projects, excluding stations, during the initial 36 months of service was determined by the JPA on a case-by-case basis and approved by each of the member agencies. The initial purchase of rolling stock, construction of stations, and other start-up costs, amounting to some $48 million, were covered primarily by Measure K funds. Station improvements are the responsibility of the county in which the station is located. ACE pays the Union Pacific Railroad about $1.5 million per year to use their tracks. ACE trains also use about 4 miles of Caltrain track in San Jose. Service began on October 19, 1998, with two daily round trips running to San Jose in the morning and Stockton in the evening. The service was named Altamont Commuter Express after the Altamont Pass through which it runs.
Service expansion

The original service used two trainsets, each with four bilevel coach cars, for a total seated capacity of 1,120 passengers in each direction daily. In September 1999, less than a year after opening, the service reached 1,000 daily riders per direction, near full capacity.
To enable more trains on the line, ACE funded $3 million in track improvements, but the limited amount of equipment allowed ACE to add only a morning "short turn" run between San Jose and Pleasanton. This "turn-back train" started service on February 21, 2000, and gave Pleasanton and Fremont a third inbound train to alleviate the crowding on the two earlier trains. Even with the added capacity, by early 2001 ACE was regularly carrying more than 700 daily standees.
ACE purchased additional equipment, allowing the "turn-back train" to operate to Lathrop/Manteca station – nearly the full length of the route – beginning on March 5, 2001. Trains also began stopping at Santa Clara station. Although the third train added 560 seats in each direction, it brought an immediate increase of 380 daily riders. ACE then planned to add a fourth round trip later in the year, with fifth and sixth round trips by 2006. However, by late 2001, the deepening dot-com recession was hurting ridership, and expansion plans were put on hold. On June 30, 2003, the ACE JPA was dissolved in favor of a Cooperative Services Agreement between the three member agencies.
On January 6, 2003, ACE introduced the Stockton Solution Shuttle, allowing Stockton passengers to use the ACE trip which terminated at Lathrop/Manteca. The rail trip was extended to Stockton on August 1, 2005. At that time, service to Santa Clara was suspended to allow for the construction of a second platform and pedestrian tunnel at the station.
On August 28, 2006, ACE added a fourth round trip, which operated midday using one of the existing trainsets. On November 7, 2006, San Joaquin County voters approved a 20-year extension of Measure K. Suffering from reduced funding due to the Great Recession, ACE cut the lightly used midday trip on November 2, 2009. On May 14, 2012, ACE restored service to Santa Clara station. On October 1, 2012, a fourth rush-hour round trip was added, running approximately one hour after existing trips.
Altamont Corridor Express
In December 2012, the service was rebranded from Altamont Commuter Express to Altamont Corridor Express to reflect plans for a broader scope of service. In March 2014, ACE opened a $65 million, 121000 sqft maintenance facility in Stockton. On July 1, 2015, management and governance of the San Joaquin passed from Caltrans to the new San Joaquin Joint Powers Authority. The SJRRC continued to handle normal operation and administration. On March 7, 2016, an ACE train was derailed by a mudslide in Niles Canyon near Sunol. The front car plunged into the rain-swollen Alameda Creek. Fourteen passengers were injured, but there were no fatalities.
ACE received Road Repair and Accountability Act funds in January 2018 to begin Saturday service. Two Saturday round trips were added on September 7, 2019. Saturday service was suspended effective March 21, 2020, due to the COVID-19 pandemic. One weekday round trip was suspended on March 23 and another on April 6. One of the suspended weekday round trips returned on May 3, 2021, followed by the fourth round trip on September 7, 2021. On November 18, 2024, the latest evening eastbound train was replaced with a mid-afternoon train.
Future plans
ACEforward
In association with the California High-Speed Rail project, ACE developed plans to upgrade and expand service. Beginning around 2008, initial plans called for the Altamont Corridor Rail Project to produce a high speed rail, branded "Super ACE", capable of halving the travel time between San Jose and Stockton.
As the high-speed rail project was scaled back and rerouted to Pacheco Pass several years later, these plans were replaced with the more modest 'ACEforward''''' program. The San Joaquin Regional Rail Commission issued a notice of intent to proceed with an Environmental Impact Statement in June 2013; this was released in 2017 and prioritized goals as either long term or short term.
Also studied were possible connections with BART at Union City or the Tri-Valley via traditional ACE rail, diesel multiple units, or bus bridges. This connection is planned to be facilitated by the Tri-Valley–San Joaquin Valley Regional Rail Authority.
The California state senate allocated $400 million in revenue from a gas tax increase to ACEforward expansion.
Valley Rail
Main article: Valley Rail (ACE)
However, during the development of ACEforward, significant financial and logistical challenges to expanding service on the existing route between Stockton and San Jose were identified, and further work on the project was halted in favor of a new Valley Rail project, focusing initially on the eastern expansion to serve commuters living in the Central Valley. ACE was awarded $500.5 million in April 2018 for expanded service to Ceres and Sacramento to provide more rail service and connections within the Central Valley. Service is expected to begin from Ceres by 2023
The Union Pacific right of way between Ceres and Lathrop will be double tracked to facilitate passenger service. platforms are being extended to accommodate longer trains.
Valley Rail also includes a project segment to route ACE and Amtrak Gold Runner along the little-used Sacramento Subdivision between Stockton and Sacramento. Six new stations would be constructed along the line with a layover facility at Natomas. Trains would run the length of the line from Natomas to San Jose or Ceres with a midday short turn to Stockton. A Draft Environmental Impact Statement was released in 2020, with services expected to begin no later than 2023. The North Elk Grove station was eliminated from planning in September 2020. The project received funding via California's Transit and Intercity Rail Capital Program in 2023, by which time the project was expected to open in phases beginning in 2025. Later that year, the estimated commencement of service to Ceres and Natomas were again pushed back to 2026, with service to Merced and infill stations opening by 2030.
Service
, ACE operates four round trips per weekday in the peak rush hour directions – westbound (to San Jose) in the morning and eastbound (to Stockton) in the evening. Trains are scheduled to make the 85 mile one-way trip in 2 hours 12 minutes, at an average speed of 39 mph. Special trains serve events at Levi's Stadium. ACE does not operate on weekends or major holidays.
Route

From San Jose to just north of Santa Clara, ACE uses the Caltrain main line (Peninsula Subdivision), shared with Caltrain and Amtrak service. From Santa Clara to Stockton – the majority of the route – ACE runs on Union Pacific Railroad freight lines. From Santa Clara to Newark, ACE uses the Coast Subdivision, then the Niles Subdivision to Niles. From Niles to Lathrop, the line uses the Oakland Subdivision. From Lathrop to Stockton, the line uses the Fresno Subdivision.
The route runs through Niles Canyon, parallel to the Niles Canyon Railway, Highway 84, and the Hetch Hetchy Aqueduct. The line passes through a 0.75 mi long tunnel which cuts off one of the canyon's horseshoes. This tunnel was modified from its original configuration to accommodate intermodal double-stack freight trains. However, this left the track in poor condition, reducing speeds from 45 mi/h to 25 mi/h in the summer and as low as 10 mi/h during the rainy season. The San Joaquin Regional Rail Commission plans to rehabilitate the tunnel.
East of Pleasanton and Livermore, the line runs through the Altamont Pass on the original Feather River Route. After crossing the California Aqueduct and the Delta-Mendota Canal into the Central Valley, skirting the southern edge of Tracy. It then turns north between Lathrop and Manteca and runs to Robert J. Cabral Station in Stockton.
Stations
| Station | Image | Location | Connections | |||
|---|---|---|---|---|---|---|
| {{nowrap | Stockton | |||||
| (Robert J. Cabral) | [[File:Cabral_Station_2.JPG | 100x100px | The arch sign at Robert J. Cabral Station in Stockton]] | Stockton | {{Plainlist | |
| Lathrop/Manteca | [[File:Lathrop-Manteca_ACE_station_2492_03.JPG | 100x100px | The platform at Lathrop/Manteca station]] | Lathrop | StanRTA | |
| Tracy | [[File:Tracy_station,_May_2022.JPG | 100x100px | The platform at Tracy station]] | Tracy | Tracer | |
| Vasco Road | [[File:Vasco_Road_station_2520_10.JPG | 100x100px | The platform at Vasco Road station]] | Livermore | WHEELS | |
| Livermore | [[File:Eastbound_train_leaving_Livermore_station,_July_2018.JPG | 100x100px | An eastbound train leaving Livermore station]] | Livermore | Amtrak Thruway, WHEELS | |
| Pleasanton | [[File:Eastbound_train_leaving_Pleasanton_station,_July_2018.JPG | 100x100px | An eastbound train leaving Pleasanton station]] | Pleasanton | WHEELS | |
| Fremont | [[File:Platforms_at_Fremont-Centerville_station,_July_2018.JPG | 100x100px | Platforms at Fremont station]] | Fremont | {{Plainlist | |
| Great America | [[File:Great_America_–_Santa_Clara_Station_2238_07.JPG | 100x100px | The platform at Great America station]] | Santa Clara | {{Plainlist | |
| Santa Clara | [[File:ACE train at Santa Clara station, September 2019.jpg | 100x100px | ACE train at Santa Clara station]] | Santa Clara | {{Plainlist | |
| San Jose | ||||||
| (Diridon) | [[File:San_Jose_Diridon_station,_November_2019.JPG | 100x100px | The San Jose Diridon station building]] | San Jose | {{Plainlist |
Tickets and fares
ACE fares are distance-based and available in one-way, round trip, 10 trip, 20 trip, and monthly passes. Unlike many of the other commuter rail services on the West Coast, ACE does not have ticket machines at stations. Passengers are encouraged to use the railroad's mobile ticketing app, but paper tickets can be purchased from agents at all stations except Vasco Road and the Santa Clara Transit Center. Also, unlike many other transit services in the Bay Area, ACE does not accept the Clipper Card.
RIdership
Rolling stock
ACE operates push-pull trains with one to two diesel locomotives and four to eight bilevel coach cars. Trains typically operate with the locomotive(s) leading westbound and the cab car leading eastbound.
ACE has ordered 17 additional Bombardier BiLevel cars (5 cab cars and 12 coaches). Deliveries were expected to begin sometime in 2021. The entire fleet of Bombardier bilevel coach cars and MPI F40PH-3C locomotives will be rebuilt, overhauled, and repainted to have a matching paint. They will then continue to operate along with the newer Siemens Charger SC-44 locomotives, which entered service in 2020.
| Model | Quantity | Number | Notes | Image | |
|---|---|---|---|---|---|
| MPI F40PH-3C | 6 | 3101–3106 | [[File:ACE Train Pleasanton.jpg | 150px]] | |
| Siemens Charger SC-44 | 6 | 3110–3115 | [[File:ACE train at Santa Clara station, September 2021.jpg | 150px]] | |
| Bombardier BiLevel VI coach | 22 | 3201–3222 | [[File:ACE train at Santa Clara station, September 2019.jpg | 150px]] | |
| Bombardier BiLevel VI cab car | 9 | 3301–3308 | 3309 was wrecked in a 2016 accident in Niles Canyon and was rebuilt into a coach numbered 3222. | ||
| Bombardier BiLevel IX coach | 12 | 3223–3228 (delivered cars) | Deliveries started mid 2022 | [[File:ACE Bombardier BiLevel IX cab car at San Jose Diridon.jpg | 150px]] |
| Bombardier BiLevel IX cab car | 5 | 3310–3314 | Deliveries started mid 2022 |
References
Notes
References
- "AAR Railroad Reporting Marks (2015)".
- "Altamont Corridor Express (ACE)". BayRail Alliance.
- "Measure K". San Joaquin Council of Governments.
- "History of ACE". San Joaquin Joint Powers Authority.
- (June 6, 2014). "2014-2015 WORK PROGRAM & BUDGET". San Joaquin Regional Rail Commission.
- (2013). "North American Railroad Family Trees : An Infographic History of the Industry's Mergers and Evolution". Voyageur Press.
- Cox, Jeremiah. (July 10, 2013). "Altamont Commuter Express on the SubwayNut". Subway Nut.
- Cabanatuan, Michael. (November 16, 1999). "ACE to Add Third Morning Train / Pleasanton-to-San Jose service will begin by Feb 15". San Francisco Chronicle.
- "History". San Joaquin Regional Rail Commission.
- White, Mike. (March 12, 2001). "4th Ace train to bolster the fleet". Press Herald.
- Bott, Fran. (March 1, 2001). "Third ACE train ready to roll". The Record.
- (August 1, 2005). "Schedule Changes will be effective August 1, 2005". San Joaquin Regional Rail Commission.
- Winkelman, Cheryl. (September 28, 2009). "Train's midday run could be over". Oakland Tribune.
- "Train Schedule". Altamont Commuter Express.
- "ACE {{!}} Altamont Corridor Express". San Joaquin Regional Rail Commission.
- (2023). "Celebrating 25 Years of Express Service". Altamont Corridor Express.
- (December 10, 2012). "SJRRC Refreshes ACE Brand with new Logo". San Joaquin Regional Rail Commission.
- Rembulat, Vince. (March 23, 2014). "ACE opens $65M state-of-art facility". Merced Bulletin.
- Sheehan, Tim. (June 26, 2015). "Valley agency takes control of Amtrak San Joaquin trains". [[Fresno Bee]].
- (March 8, 2016). "Fallen Tree Derails Train in California; At Least 9 Injured". New York Times.
- (March 8, 2016). "14 hurt as commuter train derails -- no ACE service Tuesday". SFGate.
- (January 31, 2018). "California rail providers receive $52M in state funding".
- (August 21, 2019). "ACE® SATURDAY SERVICE TO BEGIN September 7, 2019". San Joaquin Joint Powers Authority.
- (March 16, 2020). "Suspension of ACE Saturday Service". San Joaquin Joint Powers Authority.
- Holland, John. (March 22, 2020). "Coronavirus upends ACE rail between Stockton and San Jose. What riders need to know". The Modesto Bee.
- (March 18, 2020). "Important Coronavirus Update: ACE Service Adjustments". San Joaquin Joint Powers Commission.
- (April 1, 2020). "Important Update: ACE to Suspend ACE 05/06". San Joaquin Joint Powers Commission.
- (May 3, 2021). "San Joaquin Regional Rail Commission Brings back ACE 05 and Ace 06, And relaunches the Wi-Fi on the same day". San Joaquin Joint Powers Commission.
- (September 3, 2021). "San Joaquin Regional Rail Commission Brings Back ACE 07 and ACE 10". San Joaquin Joint Powers Commission.
- (October 22, 2024). "New ACE Schedule for Evening Commuters". San Joaquin Joint Powers Commission.
- Johnson, Zachary K.. (November 13, 2009). "'Super ACE' rail project touted". Modesto Bee.
- (June 24, 2013). "NOTICE OF PREPARATION OF AN ENVIRONMENTAL IMPACT REPORT". San Joaquin Regional Rail Commission.
- (May 31, 2017). "ACE expansion report released".
- (April 4, 2014). "ACEforward Alternatives Analysis and Development (presentation at SJRRC Board Meeting)". San Joaquin Regional Rail Commission.
- (July 2015). "ACEforward – Improving the Altamont Corridor Express". San Joaquin Regional Rail Commission.
- (May 13, 2020). "Valley Link Project – APTA Economic Impact Analysis".
- "Valley Link Project".
- ICF. (April 2018). "Draft Environmental Impact Report: ACE Extension Lathrop to Ceres/Merced, State Clearinghouse #2018012014". San Joaquin Regional Rail Commission.
- (April 27, 2018). "Expanded train service coming to Modesto, Merced; what it means for commuters".
- (February 8, 2017). "San Joaquin rail service plans expansion of Sacramento route". Lodi News-Sentinel.
- (January 10, 2018). "NOTICE OF PREPARATION OF AN ENVIRONMENTAL IMPACT REPORT: ACE Extension Lathrop to Ceres/Merced". San Joaquin Regional Rail Commission.
- "ACE Extension Lathrop to Ceres/Merced Draft EIR Executive Summary ES.3.1.2 Operation and Maintenance". San Joaquin Regional Rail Commission.
- (October 9, 2019). "ACE on track for Manteca & Ripon stops".
- (November 27, 2019). "SJRRC selects LAN for Altamont Corridor Express Platform Extension Project". Mass Transit.
- "Valley Rail Sacramento Extension Project Draft Environmental Impact Report". AECOM.
- (September 2020). "Valley Rail Sacramento Extension Project Draft Environmental Impact Report".
- (Jan 31, 2023). "Governor Newsom Announces Awards of $2.5 Billion for Public Transportation Projects Throughout California".
- (March 13, 2023). "ACE rail expansion runs late, just as Modesto readies its historic downtown depot".
- "Schedules". San Joaquin Joint Powers Authority.
- (August 16, 2024). "Levi's Stadium, San Joaquin Rail Commission to renew partnership for ACE special train".
- (May 9, 2016). "SUPPLEMENTAL NOTICE OF PREPARATION OF AN ENVIRONMENTAL IMPACT REPORT: ACEforward – Notice of Additional Project Element – Niles Junction Connections". San Joaquin Regional Rail Commission.
- {{CA rail schematics
- (2005). "Niles Canyon Railways". Arcadia.
- (27 May 2020). "ACE train still targeted to reach Ceres by 2022".
- (Feb 19, 2025). "Public Transportation Ridership Report Fourth Quarter 2024". [[American Public Transportation Association]].
- Van Hattem, Matt. (June 30, 2006). "Altamont Commuter Express: The commuter rail service linking San Jose and Stockton, Calif.". Trains Magazine.
- (July 2020). "2020/2021 Work Program and Budget".
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