Jacobs frames the
sidewalk as a central mechanism in maintaining the order of the city. "This order is all composed of movement and change, and although it is life, not art, we may fancifully call it the art form of the city and liken it to the dance." To Jacobs, the sidewalk is the quotidian stage for an "intricate ballet in which the individual dancers and ensembles all have distinctive parts which miraculously reinforce each other and compose an orderly whole." Jacobs posits cities as fundamentally different from towns and suburbs principally because they are full of strangers. More precisely, the ratio of strangers to acquaintances is necessarily lopsided everywhere one goes in the city, even outside their doorstep, "because of the sheer number of people in small geographical compass." A central challenge of the city, therefore, is to make its inhabitants feel safe, secure, and socially integrated in the midst of an overwhelming volume of rotating strangers. The healthy sidewalk is a critical mechanism for achieving these ends, given its role in preventing crime and facilitating contact with others. Jacobs emphasizes that city sidewalks should be considered in combination with physical environment surrounding sidewalks. As she put it, "A city sidewalk by itself is nothing. It is an abstraction. It means something only in conjunction with the buildings and other uses that border it, or border other sidewalks very near it."
Safety Jacobs argues that city sidewalks and people who use sidewalks actively participate in fighting against disorder and preserving civilization. They are more than "passive beneficiaries of safety or helpless victims of danger". The healthy city sidewalk does not rely on constant police surveillance to keep it safe, but on an "intricate, almost unconscious, network of voluntary controls and standards among the people themselves, and enforced by the people themselves." Noting that a well-used street is apt to be relatively safe from crime, while a deserted street is apt to be unsafe, Jacobs suggests that a dense volume of human users deters most violent crimes, or at least ensures a critical mass of first responders to mitigate disorderly incidents. The more bustling a street, the more interesting it is for strangers to walk along or watch from inside, creating an ever larger pool of unwitting deputies who might spot early signs of trouble. In other words, healthy sidewalks transform the city's high volume of strangers from a liability to an asset. The self-enforcing mechanism is especially strong when the streets are supervised by their "natural proprietors," individuals who enjoy watching street activity, feel naturally invested in its unspoken codes of conduct, and are confident that others will support their actions if necessary. They form the first line of defense for administering order on the sidewalk, supplemented by police authority when the situation demands it. She further concludes three necessary qualities that a city street needs to maintain safety: 1) a clear demarcation between public and private space; 2) eyes upon the street and sufficient buildings facing streets; 3) continuous eyes on the street to guarantee effective surveillance. Over time, a considerable number of criminological studies have applied the concept of "
eyes on the street" in crime prevention. Jacobs contrasts the natural proprietors to the "birds of passage", the transient and uninvested block dwellers who "have not the remotest idea of who takes care of their street, or how." Jacobs warns that, while neighborhoods can absorb a large number of these individuals, "if and when the neighborhood finally
becomes them, they will gradually find the streets less secure, they will be vaguely mystified about it, and...they will drift away." Jacobs draws a parallel between empty streets and the deserted corridors, elevators, and stairwells in high-rise public housing projects. These "blind-eyed" spaces, modeled after the upper-class standards for apartment living but lacking the amenities of access control, doormen, elevator men, engaged building management, or related supervisory functions, are ill-equipped to handle strangers, and therefore the presence of strangers becomes "an automatic menace." They are open to the public but shielded from public view, and thus "lack the checks and inhibitions exerted by eye-policed city streets," becoming flash points for destructive and malicious behavior. As residents feel progressively unsafe outside their apartments, they increasingly disengage from the life of the building and exhibit tendencies of birds of passage. These troubles are not irreversible. Jacobs claims that a Brooklyn project successfully reduced vandalism and theft by opening the corridors to public view, equipping them as play spaces and narrow porches, and even letting tenants use them as picnic grounds. Building on the idea that a bustling pedestrian environment is a prerequisite for city safety in the absence of a contracted surveillance force, Jacobs recommends a substantial quantity of stores, bars, restaurants, and other public places "sprinkled along the sidewalks" as a means to this end. She argues that if city planners persist in ignoring sidewalk life, residents will resort to three coping mechanisms as the streets turn deserted and unsafe: 1) move out of the neighborhood, allowing the danger to persist for those too poor to move anywhere else, 2) retreat to the automobile, interacting with the city only as a motorist and never on foot, or 3) cultivate a sense of neighborhood "Turf", cordoning off upscale developments from unsavory surroundings using cyclone fences and patrolmen.
Contact Sidewalk life permits a range of casual public interactions, from asking for directions and getting advice from
the grocer, to nodding hello to passersby and admiring a new dog. "Most of it is ostensibly trivial but the sum is not trivial at all." The sum is "a web of public respect and trust," the essence of which is that it "
implies no private commitments" and protects precious privacy. In other words, city dwellers know that they can engage in sidewalk life without fear of "entangling relationships" or oversharing the details of one's personal life. Jacobs contrasts this to areas with no sidewalk life, including low-density suburbia, where residents must either expose a more significant portion of their private lives to a small number of intimate contacts or else settle for a lack of contact altogether. In order to sustain the former, residents must become exceedingly deliberate in choosing their neighbors and their associations. Arrangements of this sort, Jacobs argues, can work well "for self-selected upper-middle-class people," but fails to work for anyone else. Residents in places with no sidewalk life are conditioned to avoid basic interactions with strangers, especially those of a different income, race, or educational background, to the extent that they cannot imagine having a deep personal relationship with others so unlike themselves. This is a false choice on any bustling sidewalk, where everyone is afforded the same dignity, right of way, and incentive to interact without fear of compromising one's privacy or creating new personal obligations. In this way, suburban residents ironically tend to have
less privacy in their social lives than their urban counterparts, in addition to a dramatically reduced volume of public acquaintances.
Assimilating children Sidewalks are great places for children to play under the general supervision of parents and other natural proprietors of the street. More importantly, sidewalks are where children learn the "first fundamental of successful city life: People must take a modicum of public responsibility for each other even if they have no ties to each other." Over countless minor interactions, children absorb the fact that the sidewalk's natural proprietors are invested in their safety and well-being, even lacking ties of kinship, close friendship, or formal responsibility. This lesson cannot be institutionalized or replicated by hired help, as it is essentially an organic and informal responsibility. Jacobs states that sidewalks of thirty to thirty-five feet in width are ideal, capable of accommodating any demands for general play, trees to shade the activity, pedestrian circulation, adult public life, and even loitering. However, she admits that such width is a luxury in the era of the automobile, and finds solace that twenty-foot sidewalks – precluding rope jumping but still capable of lively mixed use – can still be found. Even if it lacks proper width, a sidewalk can be a compelling place for children to congregate and develop if the location is convenient and the streets are interesting. ==The role of parks==