The Bay Area’s Most Important Rail Corridor

Jack Turner
5 min readMar 15, 2022

It’s not Caltrain

ACE train in Alviso | Photo from https://www.flickriver.com/photos/dombas/50302622358/

Though I expect to cause controversy when I say this, I can definitively say it’s not Caltrain. Caltrain is great, and prior to the pandemic saw exceptionally high ridership, but the Altamont Corridor Express (ACE) also was incredibly successful, and in my opinion, is more important as of right now. While it would be a devastating loss if Caltrain were to suddenly stop running (as it nearly did as a result of the pandemic), the ACE corridor has exceptional value for the region as more and more people move to the exurbs of the region with housing prices only going up.

The ACE train runs from Stockton in the Central Valley to San Jose, the heart of Silicon Valley, making four trips in each direction every weekday: four in the morning from Stockton to San Jose, and four in the evening back to Stockton. The train has numerous bus connections at almost every stop, and makes it very easy to get from the Central Valley to Silicon Valley. With that in mind, it might be a bit more apparent why this line is so important: it connects thousands of high paying jobs with cheaper housing, and saves significant stress, and sometimes time, as compared to those who choose to drive into the Silicon Valley on Interstate 580.

As a result of ACE’s importance to the Tri-Valley region (the Dublin/Pleasanton/Livermore area for those unfamiliar with Bay Area geography) and role as a regional connector to the Central Valley, there are a large number of projects being pursued to improve the service in future. The biggest hindrance to the service at present is the mountainous, single-tracked section over the Altamont Pass, which largely contributes to the route taking over two hours to traverse. The curvy track hinders speed, and without a second track, it is very difficult to run trains in the counter-peak direction (ie. San Jose to Stockton in the AM and Stockton to San Jose in the PM). There are plans to use more tunnels and to double track the section, which will be huge improvements that will allow for faster service and more bi-directional service. ACE also has plans to expand service towards Modesto, a city that is increasing in its role as a bedroom community for the Bay Area with its affordable housing prices (you can read my article on Regional Rail and Bay Area Super Commuting here). In the future, we will likely see ACE transform truly into a regional corridor rail service — with bi-directional, fast, and frequent trains — rather than a commuter service; indeed, the system was renamed to the Altamont Corridor Express from the Altamont Commuter Express in 2013 to reflect their desire to be more of a corridor train rather than a commuter train (although of course the system is still heavily commuter-oriented outside of its scant pre-pandemic weekend service).

Photo from acerail.com

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This article is part of a larger series of pieces covering different Bay Area transit agencies — the Bay Area is unique as there are almost 30 separate agencies covering service around the region. In other large metro areas you would normally see maybe 2–5 agencies covering a region; clearly having almost 30 unique agencies makes connections difficult, but ACE does a good job. I had the chance last summer to ride ACE for myself, and I was very impressed not only by the comfort of the trains, but also the aforementioned bus connections. In my 40 minute ride from San Jose to Pleasanton, I noticed surprisingly high post-covid ridership, gorgeous views, and a rail system well-managed overall. Though it cost me over $10 just for that 40 minute ride, a very steep price, I knew that the people around me on the train riding daily were getting cheaper tickets through passes and other deals for frequent riders.

To that point on ridership, ACE, surprisingly when I rode it, managed to attract a decent amount of riders despite the pandemic going on. Prior to the pandemic, seven or eight car trains were not uncommon as every station was packed with people waiting for the four inbound trains each morning. At one point even ACE decided to run weekend service leading up to Covid, and it is a true shame that has yet to be restored. Funnily enough, Caltrain has said that they have seen incredible ridership success on weekends, seeing more ridership than pre-Covid times. While the ACE train serves a different demographic with less frequency, I hope we could see the same results.

As affordable housing continues to increase along the I-580, I-5, and I-205 corridors, I truly believe people will see how valuable the ACE train is. Super commuting is becoming ever more popular in the region, and maximizing the available train services will go a long way to reduce the long-term effects of spending over four hours commuting per day. When comparing rail corridors, the Bay Area is seeing the largest expansion in population along the Altamont corridor, and ensuring that future rail service is effective at serving the region will be critical. ACE already has some of the best interconnectivity to the other agencies in the region, with VTA shuttles connecting to the train at all three stations in Santa Clara County, as well as local bus service as mentioned at many other stations along the route. The next couple years will be critical in ensuring that these services continue and are well-maintained. It would be ill-advised to invest in I-580 infrastructure instead which in turn makes train investment even more needed.

ACE is already a crucial piece of Bay Area Transit, and in the coming years keeping it that way will be critical to the overall health of the Bay Area.

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Jack Turner

College sophomore interested in people, places, and policy