How much parking does a DC townhome neighborhood have?

During last week’s resident parking hearing, several witnesses told Councilmember Graham that DC has too many resident permits. I decided to take a look at a typical neighborhood in Ward 1 to see how many street parking spaces there were compared to the number of homes. I selected Advisory Neighborhood Commission Single-Member District (SMD) 1D05, because from the overhead view it looked to be almost completely townhomes, simplifying the counting. Here’s the Google map I created for this study:

Results: 1D05 has approximately 1.7 on-street parking spaces per building. If every building were a one-family residence, received one RPP permit, and parked one car, there would be only 387 left to share among the 529 homes and their visitors. Other medium-density DC townhome neighborhoods, like Capitol Hill or Georgetown, are similar.

Method: Using Google Maps, I drew a boundary line around ANC1D05 using the ANC map located here. I divided up the district into 8 sub-districts and counted homes in each sub-district, counting 529 homes total. There were a couple of buildings that I was not sure were residential buildings, so I counted them as “homes”. More than one family may occupy a building, which would mean fewer parking spaces per home than I estimated. The vast majority of buildings in the district appear to be townhome-style residences.

I then used the Google Maps scale to calibrate a ruler, with every 20 feet of curb length equal to one parking space. I measured each sub-district’s block faces, assuming that the block face opposite the street (across the SMD boundary) would be used for parking other SMD’s cars. For each block face, I counted the length of the block face without subtracting any length for corners or curb cuts. That is one source of potential error, which probably overestimates the number of curb parking spaces. Since there was not an adjacent residential area on Adams Mill Road NW, I counted both sides of the street as having available curb spaces. I also double-counted the similar segment of Irving. I did not count the short segment of Mount Pleasant Street since it is commercial.

My estimate of 20 feet per car underestimates the number of spaces, since a 2009 Honda Accord can park with only 18.5 feet of space (assuming one foot gap on each end), and a 2009 Honda Civic only needs 16.6 feet with the same gaps. Therefore, the available spaces could vary by 10-15% depending on vehicle lengths. The overestimate from car size probably approximately cancels out the underestimate from assuming there are no curb cuts and that parking is allowed all the way to the corners.

Based on my estimate, the sub-district between Adams Mill Road and 18th St NW, Irving and Kenyon Streets NW (“zone 6”) has the most street parking, at 2.6 spaces per building, while the adjacent sub-district between Irving, Hobart and Mount Pleasant Streets NW (“zone 8”) has the least, with only 1.2 parking spaces per building.

On average, there are 1.7 available curb parking spaces per house in 1D05. Since the development pattern appears similar to other townhome neighborhoods in the District in terms of street grid density and average townhome size, the results should apply to those other neighborhoods, such as Capitol Hill, where most buildings are single-family townhomes with few or no curb cuts.

Contact me if you’d like the complete data.