Grids and Neighborhoods

The urbanist blogosphere, for those of you who don’t follow it, has been chattering about street grids of late, prompted by this fascinating comparison of the standard block size in various American cities. The basic argument is between those who defend a “fused grid” of some kind, which includes larger and smaller roads and a lot of three-way intersections, and the grid purists, who think that the ideal street layout is lots of orthogonal streets of the same size. Among the latter, Jarret Walker at Human Transit argues most compellingly:

Grids are easy to remember.  They fit our brains.  Anyone who’s navigated Manhattan knows that the shredded street patterns of Lower Manhattan, below 14th Street, take up far more of your brain than the uniform grid that stretches from 14th Street to beyond 125th Street.  In the latter area, which is about half of Manhattan, almost any location is easily described in terms that look like co-ordinates: Second Avenue at 73rd Street, etc.   You can hold a huge part of the map of the city in your mind with very little effort.  With those simple co-ordinates, your mind can jump to whatever location you choose, and often plot a rational course to get there.  In short, the regular gridded area feels conceptually available in a way that the labyrinth of Lower Manhattan is not.

The idea of conceptual availability is an important one, but I think it contains a glimmer of an argument against regular grids. The idea of a neighborhood, I think, denotes a relatively small group of people who feel that the streets around them are a kind of extension of their home, a space that is both public and private, a place for chance encounters with neighbors but less available to outsiders than to neighborhood members. Very frequently this unavailability comes in the form of physical barriers and actual impediments to through-traffic, as in the cul-de-sac subdivision, and clearly such entirely enclosed areas of a city can have destructive effects outside their walls. But it seems to me like slight deformations of the street grid are a powerful way of making neighborhoods less conceptually available without requiring actual barriers and their accompanying pathologies. The neighborhood with its street grid a bit differently aligned than the rest of the city’s, for instance, will be no more difficult to access than any other part of the city, but its residents will feel it to be less available to strangers than it is to them and their neighbors.

(While of course many desirable effects can be achieved by fracturing a street grid for cars while leaving it maximally available for pedestrians, I think my point holds true independent of how pedestrianized the grid is. Even if everyone travels around the city on foot, neighborhoods will benefit from being psychologically less available to city residents at large than to their members.)