A quick, visual illustration of the folly of street parking

Free, unlimited street parking in densely-populated cities is a well-intentioned but wrongheaded policy, representing a grievous misallocation of public space. Street parking in places like this is treated as if it were a public good, but this hides the very real costs paid by mostly lower-income people to maintain this good for the benefit of their wealthier fellow citizens. To understand why, it is important to take a look at the simple geometry of the issue.

Let’s take a random block in New York City, say, this one:

And here it is at street-level:

As we can see this looks like a typical New York City block — a pleasant, tree-lined residential street with prewar, walk-up rowhouses (one example bounded in a red rectangle in the aerial view) on both sides. We also notice that both sides of the street are pretty full in terms of parking, with cars nicely lined up and gaps left only for fire hydrants. This seems like a pretty neat little scene, with all the different elements having visual weight that feels intuitively right: cars and road take up maybe a quarter, pedestrian walkways maybe an eighth, trees and sky another eighth, and the balance taken up by buildings. Overall, you would be forgiven for believing that this was a sensible model for development.

However, it doesn’t take much math to demonstrate that what feels intuitively right is in fact shockingly out of whack with reality and common sense.

Along its east-west axis, this block is approximately 650 feet long. A standard US parking space is 18 feet long. New Yorkers park closer together and have smaller cars than the rest of America, but there are also fire hydrants and other No Parking areas, so let’s say these net out, allowing for a total of 36 cars to park on either side of the street. That seems like a lot of cars, but now let’s compare it with the number of residents. I count 18 rowhouses on the north side of the block alone. From the street view it looks like these are around 5 stories high and, if my experience in NYC is any guide, probably have 2–4 apartments per floor, for a total of 180–360 apartments. If we take 250 as a conservative estimate, we are then saying that under optimal conditions less than 15% of tenants can keep a car on this street, even before factoring in things like two-car households, or visitors looking for a place to park, or buildings with elevators in them.

Put another way, each of these row houses has about 10–20 apartments. If each apartment had one car, this would require 150–300 linear feet of parking, compared to the 25 feet of frontage each building has. Returning to our aerial photo from before, we can see that the one highlighted rowhouse requires 6x (thick red line) to 12x (thin red line) as much street frontage as it takes up to be able to have even one car per apartment:

If this inequality were any more visible, I doubt people would stand for it — if we designated these 10,000 square feet per block to public parks that only people in the upper quintile of income were allowed in, the outcry would be as vigorous as it would be justified. But parking often gets a free pass, because without thinking through the math it seems like a reasonable solution and a good use of public resources.

This is just another, simple illustration of how car-based transportation simply does not scale to urban environments, and how devoting more space and money to automotive infrastructure — to the detriment of public space, public transit, pedestrians, cyclists, and buildings — will fundamentally never be able to solve urban transportation problems.