A few weeks ago, Matthew Yglesias was in Somerville, blogging about how you can get a lot of density out of low-rise development. That’s an important point, and low-rise density is one of LA’s greatest strengths, something I’ll be posting on extensively here. But today, I want to talk about a reply that Aaron Naparstek tweeted:
That doesn’t seem right to me, because it’s not like you need a car to get around Inman. The residential density resulting from historic patterns of development in Somerville is not correlated to proximity to rail stops, yet everyone seems to agree that it works pretty well.
Now, along comes ACCESS and publishes an article questioning the validity of half-mile radii for TOD at transit stop. Check out Figure 1. It shows that once you go past 0.5 miles, the increase in transit ridership holds up remarkably well as distance increases. A 100-resident development will generate about 25 riders at 0.5 miles out. Move it twice as far and it still generates about 18 riders. Employment generates even more ridership and ridership holds up even better – at 100-job development at 0.5 miles will generate about 40 riders, and at 1.0 miles about 35 riders.
Not surprisingly, Figure 1 looks suspiciously like a demand curve: amount of transit demanded versus the cost (in distance) of transit. Demand is not a fixed quantity. Some people will pay more to walk less, but others will walk more to pay less. Housing and commercial space that is located closest to the transit stop is going to be the most expensive. Of course, that’s partly because it’s close, but it’s also because there’s less of it. Within 0.5 mile of a station, there’s 500 acres of land. But between 0.5 and 1.0 miles, there’s 1,500 acres of land. Given the same intensity of development, the 0.5 to 1.0 mile zone will probably generate more ridership.
In other words, if you upzone a fixed radii around your transit station, you miss the opportunity to provide housing and business opportunities for people willing to walk or bike further. In fact, you may be missing out on a majority of the ridership potential, and failing to allow development that would really help lower and middle income residents. This is a lesson that Los Angeles should keep in mind as it looks at changing the zoning around Expo Line stations.