Rules requiring a set number of parking spaces per home or per square metre of shop floor are among the least discussed and most consequential provisions in planning law.
The requirement is written before the building is designed
Zoning codes commonly specify a minimum number of spaces for each land use, and the developer must provide them regardless of whether the eventual occupants own cars.
Because a parking space with its access aisle occupies a substantial area, the requirement effectively decides how much of a site can be built on.
Architects then design within whatever remains, which is why so many buildings of a given era share a similar footprint and setback.
The cost is bundled into every unit
Surface parking consumes land that could have held housing, and structured or underground parking is expensive to excavate, ventilate and drain.
That cost is recovered through rents and sale prices whether or not a particular household uses the space, so residents without cars subsidise those with them.
Unbundling parking from rent makes the cost visible and typically reduces demand for it, which is why the practice is spreading in cities that have relaxed minimums.
Requirements were rarely based on measurement
Many standards were copied between jurisdictions with little local study, and the original figures often reflected peak demand at free parking on an unusually busy day.
Designing to that peak guarantees oversupply for the rest of the year, and the surplus is visible in half-empty lots surrounding retail buildings.
Because the requirement applies to each building individually, spaces cannot be shared between uses that peak at different times unless the code explicitly allows it.
The effect on street life is direct
Frontages given over to driveways, ramps and parking bays are frontages not given to shops, doors and windows, which is what makes a street worth walking along.
Distances between destinations grow as each building is set back behind its own lot, and longer distances make walking less viable, which raises car use again.
The requirement therefore produces the conditions that justify it, which is the central criticism made of it.
Reform is spreading but slowly
A growing number of cities have removed minimums entirely, replacing them with maximums or with nothing, and letting developers decide what to build.
Results generally show less parking built near transit and more housing on the same land, alongside genuine local disputes about street congestion.
Managing the kerb through pricing and permits is the usual complement, since removing a requirement to build parking does not remove the demand to park.