As I wrote on Monday, DC Office of Planning is considering a “buffer zone rule” that would require parking in multi-unit apartment buildings if they are within 400 feet of a low- or moderate-density residential building. As I argued, that rule is too broad.
Instead, I recommend that the rule only apply to buildings near low-density zones. OP is already proposing to require parking in R-1 and R-2 zones, so it would be most logical for the buffers to only surround those zones. Otherwise, the buffer would be effectively extending the parking requirement to denser zones anyway.
I also recommend exempting the areas around Metro stations. We’ve made an enormous public investment in Metro; we should reap the benefits by building developments near the stations that encourage people to ride instead of drive. There are plenty of driving-oriented neighborhoods; let’s not force the ones around our Metro stations to be more drivable than need be.
To illustrate the alternatives, I’ve made a set of maps showing various combinations of which zones get the buffer, how wide the buffer is, and whether Metro stations are exempted. The multi-colored map shows the low and moderate density residential zones, R-1 through R-5-B, that contain single-family and 2-3-story multi-family buildings; here is a summary of these zones. White areas represent the commercial corridors, higher density residential zones (the taller apartment building areas), and government facilities.
We really shouldn’t be creating this buffer at all. There’s no need to require parking. Even in low-density neighborhoods like Chevy Chase in DC, taller apartment buildings coexist just fine without lots of parking. Developers will want to build some parking anyway—we don’t need a minimum to convince them to build some, and if the market doesn’t make parking appropriate, the law should not mandate it.
Nonetheless, if it’s politically necessary to create these buffer zones, we should ensure they are narrowly targeted to the areas where parking spillover danger is greatest. That’s in low (R-1 and R-2) zones, when not immediately adjacent to a Metro station.