Mixed Primary Uses

Definition

Mixed primary uses is the first of Jane Jacobs's four conditions for city diversity: "The district, and indeed as many of its internal parts as possible, must serve more than one primary function; preferably more than two. These must insure the presence of people who go outdoors on different schedules and are in the place for different purposes, but who are able to use many facilities in common" (Jacobs 1961, p. 150). Primary uses are the "anchors" that bring people to a district for fixed reasons — offices, factories, dwellings, some entertainment and education; secondary diversity is the enterprises that grow in response to them. The mechanism is time: "On successful city streets, people must appear at different times." The converse is the one-shift district: lower Manhattan, 400,000 workers, whose commerce must "cram" into "some two or three hours a day" — "a miserable inefficiency for any plant" — and which loses firms to mixed-use midtown because "their personnel departments can't get or keep people who can spell 'molybdenum'" (pp. 154–156).

The concept's negative proof is the whole apparatus of orthodox planning: "the principles of sorting out — and of bringing order by repression of all plans but the planners' — have been easily extended to all manner of city functions, until today a land-use master plan for a big city is largely a matter of proposed placement… of many series of decontaminated sortings" (p. 25). Its institutional enemies are the CBD ("A Central Business District that lives up to its name and is truly described by it, is a dud," p. 165) and the decontaminated civic-cultural island ("American downtowns… are being witlessly murdered," p. 172). Its public-policy tool is the "chessman" — placing night-use primers like Carnegie Hall where they fortify and balance existing pools of use (pp. 167–169).

Key Thinkers

• Jane Jacobs — the concept's author: time-spread as the economic engine of safety, contact and cross-use (1961).
• Richard Ratcliff (not yet paged — see log) — the land economist quoted on decentralization: "Where decentralization is the product of centripetal forces, it is healthy" (p. 166).

Related Concepts

• separation-of-uses — the doctrine this concept reverses: Euclidean zoning and the Garden City's "sorting" as its juridical and ideological prehistory.
• small-blocks — condition 2: mixture fails if paths cannot physically mingle.
• aged-buildings — condition 3: the mixture needs its economic yield-spectrum.
• in-between-densities — condition 4: the mixture needs enough people to pool.
• self-destruction-of-diversity — the mixture's own failure mode: the most profitable use duplicated until the pool collapses.

Source Support

Sources in the wiki that discuss this concept:

• The Death and Life of Great American Cities (Jacobs 1961) — condition 1 stated (p. 150; Ch. 8, pp. 152–177); the Hudson Street two-shift economics (pp. 152–154); the lower Manhattan time-unbalance case (pp. 154–162); primary/secondary diversity distinction and its becoming-primary limit (pp. 162–163); Carnegie Hall as primer and Lincoln Center as decontamination (pp. 167–169); the Pittsburgh/Oakland double unbalance (pp. 170–172); the courts-and-opera muddle (pp. 173–175); Harlem as the residence-without-work cautionary case (p. 175); the "witlessly murdered" downtown diagnosis (p. 172).
• Dark Age Ahead (Jacobs 2004) — the concept's performance-regulation corollary: zoning's third founding assumption — "The mingling of commercial or other work uses with residences is bad" — named among the "rejections of cities and city life, devised by utopians and reformers" (p. 153), against the civic-behavior finding "In cities, differing uses in close proximity tame one another" (p. 156); the caution that even concentrated genteel uses misbehave ("Even concentrated genteel concert and theater centers from which hordes of people emerge simultaneously, all wanting to nab taxis or buy a drink, breed pushiness and other bad manners," p. 156); and the performance code as the instrument that permits mixture by regulating outcomes — decibels, pollution, frontage, scale — instead of uses (see performance-codes).

Source Support linking rule: All entries in this section must be wikilinks to source note pages in wiki/source-notes/ using the source-notes/ path prefix. Never link to raw files — raw files are not wiki pages.

This page requires fuller treatment — created at the Jacobs ingest; awaits the mixed-use land-economics literature and the later critique of Jacobs's consumerism (Sennett, Harvey).

Open Questions

• Jacobs's effectiveness test is concrete: mixed users must "actually use the same streets" and share some facilities (pp. 162–163). Does the mixed-use development of today — the residential tower over the ground-floor retail podium — pass her test, or is it the "corner grocery gimmick" (p. 190) at scale?
• Her claim that residence "must necessarily be a manifestation of district vitality, rather than a cause of it" (p. 160) inverts the contemporary downtown-housing gospel. What evidence base does the wiki hold for either direction of causation?