As part of the debate over Washington, DC’s resident permit parking program, the issue of maximum allowable permits came up during the recent Performance Parking Hearing chaired by Councilmember Graham. 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:
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Results: ANC1D05 has approximately 1.7 on-street parking spaces per household. If every household were to receive one RPP permit and park one car, there would be only 387 left to share among the 529 homes and their visitors. This result is likely applicable to most DC townhome neighborhoods.
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”. The result may be that more than one family occupies the building, meaning that the results will be non-conservative (fewer parking spaces per home than 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, so that is one source of potential error in that it would overestimate 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. The similar segment of Irving Street NW was also double-counted. I did not count the short segment of Mount Pleasant Street since it appeared to be commercial.
My estimate of 20 feet per car is somewhat non-conservative, since a 2009 Honda Accord can be parked in 18.5 feet (assuming one foot gap on each end), and a 2009 Honda Civic can be parked in 16.6 feet with the same gaps. These representative vehicles show that the average vehicle length and parking habits in a neighborhood can vary the available spaces by 10-15%. This error is similar in magnitude to the error in assuming there are no curb cuts and that parking is allowed all the way to the corners.
My estimates of available parking spaces show that the sub-district between Adams Mill Road and 18th St NW, Irving and Kenyon Streets NW (“block 6”) is the most adequately supplied with street parking, at 2.6 spaces per household, while the adjacent sub-district between Irving, Hobart and Mount Pleasant Streets NW (“block 8”) is the most under-supplied, at only 1.2 parking spaces per household.
The data show that on average, there are 1.7 available curb parking spaces per house in the SMD. 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 appear to be applicable to those other neighborhoods, such as Capitol Hill, where the development style is townhomes and curb cuts are not prevalent.
The data is available upon request.