Parking regulation looks like a technical matter and turns out to have determined a great deal about how cities look, what housing costs and how people travel.
The minimum requirement
Most planning codes adopted requirements that new development provide a minimum number of parking spaces per unit or per floor area.
The stated purpose was preventing new development from overloading street parking.
The ratios were generally derived from observed peak demand at sites with free parking, which is a circular basis — measuring demand where the cost is zero and treating the result as a requirement.
What it cost
Structured parking is expensive to build, and underground parking considerably more so.
Which means the cost is embedded in the price or rent of whatever was built, whether or not the occupant owns a vehicle.
Studies estimating the cost per space, and its effect on housing affordability, have found substantial figures, particularly in dense areas where land is expensive.
The people least likely to own a car — lower-income households — pay for parking they do not use through their rent.
The land use effect
Requirements consume land that could hold buildings.
Which reduces density, increases distances, and makes walking and transit less viable, which increases car dependence, which appears to justify the requirement.
That feedback loop is the central argument of the academic literature on this, and it has been influential enough to change policy in a number of cities.
What happened when requirements were removed
Numerous cities have eliminated or reduced minimums over the past decade.
Evidence from those changes generally shows developers building less parking than the previous minimum, which indicates the requirement was binding.
Predicted street parking chaos has generally not materialised at the scale feared, particularly where street parking was also managed by pricing.
The housing effects are harder to isolate, since parking reform generally accompanies other changes.
Pricing street parking
The complementary reform and the more politically difficult one.
Free or underpriced street parking produces cruising for spaces, which generates traffic and emissions.
Studies measuring the share of urban traffic that is cruising for parking have found substantial figures in busy districts.
Demand-responsive pricing, adjusting rates to maintain a target availability, has been implemented in several cities with measurable reductions in cruising.
It is unpopular because it converts a free good into a priced one, which is politically costly regardless of the efficiency argument.
Maximums
Some cities have gone further, capping rather than requiring parking.
Generally in areas with good transit, on the reasoning that abundant parking induces driving.
Evidence on induced demand from parking supply is reasonably consistent, following the same logic as induced demand from road capacity.
Where the disagreement is genuine
Reform assumes alternatives exist. In places with poor transit and dispersed development, removing parking without providing alternatives shifts costs onto people with no other option.
Which is a legitimate objection and it points at sequencing rather than at the principle.
Accessibility parking is a separate matter entirely and is generally protected and expanded in reform packages, though implementation varies and disabled people's organisations have raised real concerns about how reforms have been applied.
Residential permit schemes
The common intermediate approach.
Residents purchase permits for street parking, generally at prices well below the market value of the space.
Which manages allocation between residents and visitors and does little about total demand when permits are cheap and unlimited.
Schemes limiting permits per household, or pricing them by vehicle size or emissions, have been introduced in several cities with measurable effects.
Delivery and loading
An increasing pressure as parcel volumes have grown.
Delivery vehicles double-parking because loading bays are occupied is a significant source of urban congestion.
Dedicated loading provision, timed restrictions and consolidation centres have all been trialled, with consolidation showing promise and requiring coordination that is hard to organise.
The transition question
Electric vehicle charging has introduced a new claim on kerb space.
Which is genuinely difficult in areas without off-street parking, where residents cannot charge at home.
Solutions include lamp post charging, cross-pavement channels and dedicated bays, each with drawbacks around pavement obstruction and equitable allocation.
Data
Much parking policy has historically been made without measurement.
Occupancy surveys, which count how full streets actually are at different times, frequently find utilisation well below what residents perceive.
Which does not resolve the disagreement, since perception of scarcity at the times people want to park is what drives the politics.
Sensor-based and camera-based occupancy measurement has made this considerably cheaper to establish, and publishing the data has changed some debates.
Retail concerns
Business opposition to parking removal is consistent and rests on an assumption about how customers arrive.
Surveys repeatedly find that retailers overestimate the proportion of customers arriving by car, sometimes substantially.
Studies of streets where parking was replaced with other uses have generally found trade maintained or improved, though results vary by context and the research is contested.