If you’re into urban design, you know how important the street grid is. Indeed, those responsible for original street patterns achieve a kind of immortality – even if we don’t know their names. We certainly live with the consequences. The connectivity of streets alone determine so much about the subsequent efficiency of our transportation options. Or, as Larry Frank has demonstrated, even our weight.
So these maps, developed by Seth Kadish from Portland, Oregon, comparing the street grids of two dozen urban centers across the U.S. and Europe, tell us so much.
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The graphs, which plot the orientations of every road in a county or city, reveal just how much that region conforms to a street grid. In each graph, the tallest bar indicates the direction that more roads point to than any other direction. To ensure rotational symmetry in the graphs, each road is plotted to run in both directions, regardless of whether they’re actually one-way or two-way.
As you can see below, Cook County, Illinois (Chicago) has a particularly pronounced grid. While San Francisco county (above) has a strong grid, there’s also a substantial number of streets oriented in all sorts of directions.
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For Manhattan, we see the dominance of horizontal streets over vertical avenues — though as the graph shows, neither truly runs North-South or East-West. And European cities, not surprisingly, are far less orthogonal.
The oldest cities radiate outward from focal points. Those standing on a circle are all equidistant from the centre. Rectangular grids are a very different development style.
I read somewhere that 75% of blocks in Cook County have the long axis running east-west. The rose diagram would suggest more of a 50-50 split. I think this apparent contradiction is due to the shape of the county which, like Manhattan, is really elongated in the northerly direction.
The question to me is, given the neutrality of a grid’s orientation, why would three times as many blocks run one way and not the other? (A casual glance at Vancouver’s map shows a similar pattern outside the core, which runs at an angle to cardinal compass directions.) The answer likely lies in allowing solar access to the most properties.
Early Vancouver was built facing the water. As the trees were felled new streets were built parallel to the old ones. We lucked out with southern exposure. Burrard Inlet and the Fraser just happen to “flow” westward.
In New Westminster the result of facing the water is a diagonal grid when compared with Vancouver and Burnaby.
In Seattle you also see blocks aligned with the water, but their waterfront runs generally N-S resulting in far more N-S streets than E-W ones per square mile. Like Vancouver the downtown core parallels a short stretch of waterfront and is at an angle to the rest of the city.