This is a map of the Bay Area Rapid Transit network:

And this is an elegant visualization by Ray Luong of ridership levels over the course of one day: February 4, 2016. If you can’t see the embedded video below, click here.

[youtube https://www.youtube.com/watch?v=owGgbAS7Wq8?rel=0&w=560&h=315]

Note how the lines speed up as they go through the Transbay Tube connecting San Francisco and Oakland. That’s actually what happens. Within the 10 km-long tube, the trains reach ~130 km/h, which is more than twice as fast as the average speed throughout the rest of the network.

Recently Priceonomics posted a piece on San Francisco’s “rent explosion.” In it, was the infographic above showing the median rental rate for a 1 bedroom apartment in the city. The most obvious takeaway is that San Francisco is real expensive. In the core of the city, you’re easily looking at $3,000 per month.

That is with one exception: the Tenderloin (the green area just northwest of SOMA in downtown). The first time I ever visited San Francisco, I actually stayed on the outskirts of this area, which is a neighborhood well known for seediness, homelessness, crime, drug trade, strip clubs, and so on. And it was actually named after a similar neighborhood in New York that was also a center of vice in the late 19th and early 20th centuries.

But when I saw this diagram, I immediately asked myself: How could it be that the Tenderloin was holding out so well against the forces of gentrification? How is this island of seediness being preserved in the center of downtown? Particularly in a city like San Francisco where there’s a perpetual housing supply shortage and lots of wealth. The Tenderloin has some of the lowest rents in the city.

So I tweeted the good folks at Priceonomics and they responded with this article. It’s a few pages long, but the reasoning seems to come down to the following: active community groups that fought to keep developers out of the area (and that also own many of the buildings), downzoning, and a high percentage of rooming houses. According to that same article, the Tenderloin contains approximately 100 single room occupancy residential hotels (or SRO’s as they’re called). These were initially built to house the city’s transient and seasonal population after the great fire of 1906.

So it would appear that there are some significant barriers to entry.

But at the same time, it generally seems like a bad idea to concentrate poverty, homelessness, drug users, and so on. Interestingly enough, the article talks about how when the Bay Area’s transit system went on strike for a period of time, the supply of drugs actually dried up in the Tenderloin. This underscores how regional the drug business is, but also makes me think that dealers are almost surely benefiting from the clustering of their client base.

In any event, this is a much larger problem than just a real estate development one. I don’t know what the solution should be, but I’m pretty sure that things are being made worse by concentrating everything in one neighborhood and by rising income inequality in the city. Inequality seems to lead to all kinds of negative externalities and, from my experience, mixed-income neighborhoods perform better than 100% poor ones.

A couple of months ago I had coffee with an urban planner who had recently relocated from the Bay Area back to Toronto. One of the interesting things that came up during our conversation - that I hadn’t really given a lot of thought to before - was how corporate shuttle buses (from the likes of Apple, Google, Facebook and so on) could be impacting cities.

On the surface, they seem fairly benign. Most of the big tech companies are located outside of San Francisco, but young smart people today like living in cities. So let’s run shuttles buses that take people back and forth. Employees get to live the life they want and employers get broader access to human capital. It seems like a win-win.

But in reality, some argue that these shuttles buses reinforce a powerful trend already plaguing the region: The alienation of non-tech people. George Packer of the New Yorker called the buses "a vivid emblem of the tech boom’s stratifying effect in the Bay Area."

What I wonder though is to what extent these buses are not just an emblem, but an actual driver of stratification and other negative outcomes. The first concern that comes to my mind is the possibility for this to lead to infrastructure disinvestment. Already there seems to be a philosophical divide around transit (see BART strike).

Wired just published an interesting set of maps that try and map “Silicon Valley’s gentrification problem through corporate shuttle routes." They’re worth checking out. It’s also interesting to see how they collected the data; it was a fairly messy process.