Zoning laws in California usually require new developments to come with a minimum number of parking spaces. Housing, restaurants, stores, movie theaters — everything requires some number of parking spaces, theoretically based on the best available data.
Usually that data is whatever is listed in the Institute of Transportation Engineer’s (ITE) Parking Generation Manual. Since that manual has long been the only source of data on parking usage in the country, planners rely on it to help them figure out how many parking spaces a project should include.
But there are serious limitations with the ITE data, as is noted in the manual itself. As Professor Donald Shoup, UCLA’s “parking guru,” explained in a paper [PDF]: Providing too much parking encourages driving, thus contributing to congestion, and discourages walking and bicycling (unless you love walking across hot expanses of pavement to your store).
Plus, building parking is expensive.
A new tool, the GreenTRIP Parking Database, can help by providing better data on actual parking usage at multifamily housing units. This is only one of the many land use categories about which planners seek data, but it is a key one.
The database, created by TransForm, an Oakland-based advocacy group that focuses on better land use and transportation policies, tracks more than just parking usage. Data is available about the number of parking spaces per unit, how much of that parking sits empty, what percentage of the building is affordable housing, whether residents pay for parking separately from their rent, what level of transit service is available nearby, whether residents are offered transit passes or carshare membership, what if any parking management exists on surrounding streets, and other data relevant to parking usage.