Minimum parking requirements are a major problem for cities around the world. Minimum requirements lead to lots and lots of free parking, which in turn leads to more driving, more pollution, higher housing costs, lower quality urban design and oodles of other problems. (See this paper for details, or read the book.) One of the challenges with reforming parking minimums is that too many people worry that no one will ever build parking again ever and no one will ever again be able to find a place to park. But people worry too much about the parking supply in the future even when the evidence is overwhelming that there is more than enough parking already built.
In order to get to sane parking policy we have to come up with some way to reduce the amount of parking required through the zoning code. One promising way to support such a transition is to take advantage of existing, underused spaces. In some European cities developers have to do a parking inventory near any proposed development. Then developers contract with owners of existing parking nearby instead of building new parking capacity. You can read about various European strategies in this nice report from ITDP. Expanding on the idea that existing parking can be better utilized, a UK company called ParkatmyHouse has a service where you can sign up and offer your unused parking to people who will rent the spaces through the website. BMW iVentures likes this idea so much they just invested in the business. This is a promising way to transition from too many spaces required to better management of parking facilities. A firm like ParkatmyHouse can assemble the multitude of available spaces in a way that no individual owner will, resulting in high overall occupancy, more efficient uses of available spaces and fairer pricing of parking and development. American cities should figure out how to adapt this business model in order to institute real parking reform.