The amount of space American cities devote to parked cars is a consequence of rules requiring it. Those rules were written into zoning codes and applied for generations.
Minimums were set by formula
Zoning codes commonly required a specified number of parking spaces per dwelling, per restaurant seat or per unit of floor area, varying by use.
The figures were drawn from surveys of demand at existing suburban sites, generally measured at peak times with parking supplied free of charge.
Because they were designed to satisfy the busiest hour with no pricing, the resulting requirements produced supply that sits substantially empty most of the time.
The requirement determines the building
Parking consumes a large area per space once circulation is included, often more floor area than the dwelling it serves.
On a constrained site, meeting the requirement can make a project impossible, so the parking rule effectively sets the maximum density regardless of what the zoning allows.
Structured and underground parking are far more expensive than surface lots, which is why requirements push development towards low-density forms with open parking around them.
Costs are bundled into rents
Parking built to satisfy a requirement is paid for by the development and recovered through rents and prices, whether or not a particular resident owns a car.
Bundling makes driving appear cheaper than it is, since the cost of storage has already been paid and is not attached to the decision to drive.
Unbundling, where parking is rented separately, changes the calculation visibly and generally reduces the number of spaces households choose to hold.
Street design followed the same logic
Wide roads and generous turning radii were specified alongside parking to accommodate expected vehicle volumes, and those dimensions determine how a street functions.
Distances between buildings increase as parking is placed between them and the street, which lengthens walking trips and reduces the viability of transit stops.
The pattern reinforces itself, since a place that is difficult to reach without a car generates the driving demand that justified the parking in the first place.
Reform is now widespread
A growing number of American cities have removed minimums entirely or in transit-served districts, leaving the quantity to developers and lenders to determine.
Removal does not eliminate parking, since buildings still provide what buyers and tenants want. It ends the requirement to provide more than the market supports.
Pricing kerbside parking according to demand addresses the other half, since free street parking undermines any attempt to charge for off-street spaces nearby.