From Atlantic Cities: Mapping the Subtle Science of Parking Demand.
A new downtown condo winds up with too much parking. A multifamily apartment near a subway stop gets way too much. Even a low-rise suburban development likely doesn’t need quite such a sea of asphalt.
But we overbuild parking because that’s the way we’ve been doing it for years, and because the people who finance new developments fear what sounds like a risky investment: the transit-oriented development with hardly any parking at all.
The alternative isn’t simply to err on the other end of the spectrum; underestimate parking demand, and you wind up with equally real complications (and angry neighbors). So how do cities and developers get this right? How could they treat parking demand as a subtle science – with overlapping variables based on land use, transit access, demographics, jobs, rent pricing – instead of as an assumption?
The King County Metro Transit agency in the Seattle region has been working on this, with the help of the Center for Neighborhood Technology and the Urban Land Institute Northwest. They’ve spent the past year trying to measure exactly which factors dictate residential parking demand around the region, in downtown Seattle, in urban neighborhoods, in the suburbs and even farther out. The result of their efforts is this Right Size Parking Calculator web application that can estimate parking demand down to a single parcel of land (and that should be replicated in other cities):
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I think you’ve hit it when you say that there would be angry neighbours if you underbuild parking.
i.e. better to err on the side of caution than create an unworkable situation that cannot be easily fixed.
Aside from the visual blight of surface parking lots (which many aren’t building now) – extra parking is really just a hit to the developer, property owner or the condo owner as to whether “value is being maximized”. In most condo towers, there are enough rentals (with multiple occupants each having a car) that unused spaces can be rented out and the space would represent latent value until the condo is resold. i.e. the absence of parking is more likely to be a deal breaker than the presence of parking.
I think it’s really just an academic argument that these tings need to be “right-sized”. And there’s a question as to what “right-sized” means. Do you build for the maximum demand or the average demand. If you build for the average demand, you’ll have a lot of angry people during peak times.
As a side note, a realtor told me that the waiting time at Jameson House’s automated parking garage elevator can be 45 minutes on a busy Friday night.
Here in the UK we (WSP transport consultants) have made attempts to demonstrate a disconnect between car ownership and car travel with respect to residential parking.
Basically we’re saying that just because you own a car and want a residential parking space doesn’t mean you will drive more. Our census data married with recent traffic growth trends (negative growth) show there is merit in this arguement. Persuading the planning authorities of this with strong evidence is the key to unlocking viable developments.
Paul