Except for grains of sand, a billion of anything is a lot. That’s the total number of parking spaces that occupy the U.S. More than 200 million cars operate in this country today, so at any given moment more than 75 percent of parking spaces go unoccupied. We’ve grossly miscalculated the need for parking. In many markets, car-centric development and zoning-based parking requirements have left the landscape a wasteland of lonesome pavement. As the sharing economy grows and cities invest more in public transit alternatives, parking needs will continue to shrink.