A downtown subway grid

Recently, the SFCTA, SFMTA and various other transportation organizations released a website called Subway Vision. It aims to collect ideas from everybody about where to install new subways in SF. The Subway Master Plan is supposed to ensure that we are always building a subway, and we currently have the Central Subway under construction, along with planning for the M subway and construction hopefully in the not-too-distant future. Future expansion plans are also being considered right now, as the Rail Capacity Strategy report released back in February gives an outline of what Muni thinks its next steps will be.

People spend a lot of time talking about Geary whenever new subways are discussed. And that’s great! Having high-capacity transit on Geary is extremely important given that its bus lines ferry the same ridership as Caltrain. BRT will definitely help, and we’ll see how this develops in the future. However, I think the need for new subways downtown is often overshadowed by this discussion. Our current rail network has one subway that goes from downtown outwards, through which a large percentage of its 150,000 daily riders go. This is a huge bottleneck! Problems that occur in the subway here are liable to delay many people and cause lots of gaps and bunches. If there is one thing we can learn from New York here, it is that these problems are way more tolerable when there is some redundancy.

Having extra subways parallel to the Market Street Subway downtown is hardly a new idea. SPUR advanced the idea in this report and has implied it in various materials concerning a second Transbay Tube. By pulling together some ideas from these and the Rail Capacity Strategy, we can come up with a nice grid-like structure for subways in downtown SF.

First, if we look at the Rail Capacity Strategy, we find that Muni eventually wants to put LRT on Geary. LRT will improve capacity even more than BRT, but the most interesting part about the plan is the fact that it might be a hybrid subway/surface line. Muni gives cost estimates for all of the involved projects in the report, and the lowest estimate for Geary LRT appears to be the cost of installing surface rail along its entire length at a cost of about $1.4 billion. By using the estimated cost of installing other subways and doing some math, we can figure out that the $3 billion upper bound makes sense if Muni installs a mile of subway and 5 miles of surface rail. One mile of subway takes us from Market to about Van Ness along Geary, which is a reasonable option.

But why should we stop at Market? Merging into the Market Street Subway is probably not feasible, since it’s not possible to fit a flyover junction when there is already another subway below. Even if it were possible, it would probably be ill-advised, as we’d get one extra stop at the expense of subjecting the new subway to all of the same problems we get by combining the other lines. But there are other options—the report also has lots of figures for job and population density in various sections of the city, and we can use those to extend the route. 2nd St in particular has a very high density of both, and a subway in the Geary area could connect through Mongtomery Station and continue into SoMa along 2nd St. This line could be anchored at AT&T Park, which is surrounded by a commercial district, and which often relies on the easily-overwhelmed Muni Metro Extension to get people in and out on game days. 2nd St is also slated for an upgrade to LRT in the distant future, according to the Rail Capacity Strategy.

It might seem like overservice, and while the redundancy with the Central Subway is nice, that’s not really what we’re after. The grid really comes together when we install a subway along Folsom. Folsom is considered one of twelve high-priority corridors for expansion by Muni. By pulling a line out of the Market Street Subway between Church and Van Ness and instead sending it up Folsom, we solve a number of problems:

  • Fewer lines are merging at Van Ness, which means we can mitigate a bottleneck there
  • The already-existing flyover junction would make construction of the other one less disruptive, since we wouldn’t have to reconfigure the current subway
  • In the event of backups in the Market Street Subway, all KLM trains could reroute into the Folsom Street Subway instead, mitigating delays (J and N trains could stop at Church & Duboce for transfer) and still allowing decent access to Montgomery and Powell areas via the 2nd/Geary and Central Subways

In this proposal I choose the L train to be pulled out in standard service because we can’t pull out the J or N, as the new trains will leave the MSS before the J or N merge in; the M is going to improve capacity in the MSS after its subway expansion and use of longer trains, which is important; and the K can only run short trains at the time being, and may still be used to serve the Muni Metro Extension.

The end result is a grid-like structure centered on 2nd, 4th, Market and Folsom Sts, with additional transfer points along the Embarcadero and on King. Here’s what it looks like:

Above-ground stops are circled with gray, and Van Ness BRT is shown as the green dashed line.

There’s also room for further expansion: Leavenworth, Civic Center and 7th St stations all line up quite nicely, for instance (and would be easily connected by the bus I laid out in earlier articles). If the Caltrain railyard is rebuilt underground and the 280 spur is at least partially torn down, this could open up enough land that extending the Muni Metro Extension out to 7th St and building more rail along 7th St makes sense, as well. Some ideas for extending high-capacity transit along Van Ness send it down 11th St and Potrero Ave, in which case they would also fit nicely into this grid; extensions down Mission could also use the transfer to the new station at Duboce Ave. Sadly, I think the Chinatown T stop is too far north to have a really easy transfer, but a line down Sacramento St might be useful and connect Van Ness BRT with Embarcadero and Main St Stations. The T would be within reasonable walking distance of such a line.

This expansion provides a lot of extra options for people to move around on corridors that Muni considers important, and getting them into a shape where they work well together. Having redundant infrastructure makes the system more resilient and also makes it easier to justify arbitrary planned service changes, which people will need to deal with if we ever eventually want 24-hour rail service.

But don’t just take my word for what subways are worthwhile to build. With Subway Vision, Muni is giving all of us an opportunity to influence the evolution of the city. We should use this opportunity to tell them what we think!