An attractively designed but sparsely used “public use space.” Photo by sevenblock on Flickr.

The Montgomery County Planning Board reviewed proposed zoning rules yesterday that would create transit-oriented mixed-use (“TMX”) zones. It’s a good idea, but as written, it will also encourage building low-density, auto-oriented development in areas far from transit.

How did that happen? First of all, the TMX zones don’t just apply around Metro stations or even bus hubs. They also apply to planned stops for BRT lines. Unfortunately, there’s a long history of planning transit lines and then not actually building them. There’s a real danger that we’ll get development in these TMX zones but no transit.

Building in anticipation of future transit isn’t such a bad idea, though. In the early 1900s, governments ran transit lines out to farmland (like the Upper West Side and the Bronx in New York), and dense, walkable development followed. Today, development generally far precedes transit lines. Until we change that, it makes sense to create zoning that at least ensures that greenfield development is designed a walkable community. Then, if and when we build a transit line there, there’s some density to put the stop among instead of just endless single-family homes where all you can build is a park-and-ride.

Plus, having built-in riders helps a lot if we stay stuck with today’s federal funding formula. That formula discounts potential future development, instead prioritizing funds that move existing residents long distances. As long as we have that formula, the best way to get a transit line funded is to already have the residents in place.

Unfortunately, the proposed TMX zones don’t ensure we’ll get walkable communities. Developers get to pick a “standard method of development”, which is a low-density form with freestanding buildings, and an “optional method of development,” which allows higher density. Both the standard and optional methods include some decent design principles, like facing buildings to the street, including sidewalks, and putting parking behind or underneath buildings. But both also require “public use spaces” which usually end up as empty plazas in the fronts of buildings, creating voids, and lots of parking.

According to Christopher Leinberger, an FAR of 0.8 is the minimum for “walkable urban development.” 0.8 gets you a walkable but low-density village. The “optional method” requires an FAR of 3.0, but the “standard method” allows FARs from 0.25 to 0.5—too much for an auto-oriented suburban design, but not enough to create a walkable community. The most common example of development with that intermediate FAR is the suburban office park, two-story office buildings surrounded by parking lots a few times the footprint of the buildings and the occasional, sparsely used public park unconnected to much else. In other words, we’ll get the Shoreline area of Mountain View, California.

The Action Committee for Transit is fighting the bad parts of TMX zones.

David Alpert created Greater Greater Washington in 2008 and was its executive director until 2020. He formerly worked in tech and has lived in the Boston, San Francisco Bay, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.