A 66-acre downtown core, 96 parcels, eighty years. No parcel is cleared by hand. Each redevelopment solves the same equation the zoning code sets — fit a building and its required parking onto one lot — and the crater is what the equation returns.
Timeline
The ratchet
↻ The requirement is raised
The core, measured
Downtown land, 1950–2030
Hartford, Connecticut is the best-documented case, thanks to Norman Garrick and Christopher McCahill at UConn, and it is also the first American city to abolish parking minimums outright.
7.5% → 22%
Share of downtown Hartford's land given over to parking between 1960 and 2000, as the space count went from about 15,000 to about 46,000. Citywide, land used only for parking nearly tripled.
McCahill & Garrick, Parking and urban vitality: a tale of two cities
53% → 73%
Hartford residents commuting by car, 1960 to 2007. Over the same decades Cambridge, Massachusetts held its parking growth down and went the other way, from 42% to 38%.
McCahill & Garrick, as above
$1,200
Annual property tax lost per downtown parking space — roughly $50 million a year against the $75 million that downtown buildings generated. Hartford dropped its minimums citywide in December 2017.
Garrick et al. (2014), via CNU Public Square; Streetsblog USA
The equation on screen. For a parcel of land area A with n stories and
a requirement of R spaces per 1,000 sq ft, surface parking at 330 sq ft per space leaves achievable floor
area F = 0.9·A·n / (1 + 0.297·R·n). On a 22,500 sq ft parcel at six stories that is 121,500 sq ft when
R is zero, 26,600 at R=2, and 14,900 at R=4 — by which point 88% of the lot is
pavement and the project stops penciling as a building at all. That is the whole mechanism. Nothing about declining
downtowns, suburban competition or urban renewal is needed to produce the crater, which is the point worth making in
class: those forces were real, and the code would have done this anyway.
Where the repeal evidence lands. Turning the 2017 switch off lets you show the counterfactual side by side. In the real cases, removing the floor does not rebuild a downtown quickly: Seattle built about 40% less parking over five years and saved roughly $537 million, London's supply fell to 52% of the old minimum, but Washington DC and Grand Rapids saw developers keep providing more than the former minimums. The distribution gains a long left tail; the median developer still builds parking.