How much parking is too much parking?

We've been beating the drum for a long time about the harm that North America's epidemic of excess parking does to our cities and towns. A parking lot that's sitting empty is just about the least valuable thing you can do with a piece of land. These asphalt craters take land out of your city's tax base, push productive land uses (that is, places people want to be) farther away from each other, raise the cost of housing and consumer goods, and impede walkability.

Yet cars aren't going away anytime soon in American cities, and the people who own them generally at least demand to have somewhere reliable to put them at night. This is why, while it's often not too hard to convince people that your average Target or Home Depot or Cabela’s could stand to shrink its sea of parking, when it comes to residential building, the average person is often resolutely unconvinced by our (and many others') call to #EndParkingMinimums. If we don't make the developers build parking, won't all these people just park on the street? In front of my house and my neighbors' houses? Taking away space that we need for our own cars?

Planners at the Metropolitan Area Planning Council in greater Boston wanted to make sure they had the right answers to these common criticisms. So they've put together a remarkable report that pretty authoritatively answers the question: Are apartment buildings in greater Boston providing too much parking?

The answer: Yes.

How much too much? Read on, from the study's Executive Summary:

We interviewed property managers and conducted overnight counts of parking spaces and parked cars at nearly 200 multifamily residential developments in 14 municipalities.... The survey included apartments and condos, large and small projects, and projects close to and far from transit. Counts took place during peak utilization hours: in the middle of the night on weeknights, and not during the summer or near major holidays. Over two phases of research, we obtained data from 189 sites across the study area. The sites included 19,600 housing units, most of which have been built since 2000, and all of which provide off-street parking. In the vast majority of developments we studied, the average parking use was less than one space per household, and across the entire sample, only 70 percent of the available spaces were full when surveyed. Overall, 30 percent of the available parking we surveyed was not being used. At a quarter of the sites, less than half the parking was occupied. MAPC counted nearly 6,000 empty parking spaces—over 41 acres of pavement— representing an estimated $94.5 million in construction costs (or about $5,000 per housing unit in the survey).

Don't believe us? Head on over to the Perfect Fit parking study page they've put together and you can explore all of the data yourself, as well as a flashy interactive slide show that's perfect for illustrating the stakes of the issue to the parking-reform skeptic in your life.

If You Build It, They Will Come (to a Point)

The MAPC study didn't just count parking spaces and quantify the over-supply. They also did a statistical regression analysis to figure out which factors, if any, seem to have the strongest effect on how much parking residents use. The three that came out on top were:

Access to good transit (the more jobs available within a 30-minute commute, the less people used parking)

Percentage of deed-restricted affordable units (these low-income households averaged 0.55 cars per household parked overnight, instead of 0.7)

The amount of parking supplied

Whoa, whoa, whoa, say what? Tell me more about that last one:

In fact, supply (spaces per unit) was the single biggest predictor of demand, suggesting that the availability of parking is attracting car-owning households and influencing their behavior. The more parking is provided, the more likely it is that a household will use it.

This is the devilish thing about America's parking addiction: it's self-reinforcing. When we make it easy and free (read: subsidized) to park your car, we're not just catering to the preferences of drivers. We're also making it a bit more likely that people will choose to be regular drivers.