A Look at Street Network Orientation in Major US Cities (geoffboeing.com)

Geoff Boeing, a postdoc in the Urban Analytics Lab at the University California, Berkeley, has published a blog post that offers a fascinating look at the street orientation of major cities in the USA and around the world. What is interesting in his findings is how cities from different historical periods form different patterns, and also just how uniformly grid-structured most American cities are. From his post: In 1960, Kevin Lynch published The Image of the City, his treatise on the legibility of urban patterns. How coherent is a city's spatial organization? How do these patterns help or hinder urban navigation? I recently wrote about visualizing street orientations with Python and OSMnx. That is, how is a city's street network oriented in terms of the streets' compass bearings? How well does it adhere to a straightforward north-south-east-west layout? I wanted to revisit this by comparing 25 major US cities' orientations.

Each of the cities is represented by a polar histogram (aka rose diagram) depicting how its streets orient. Each bar's direction represents the compass bearings of the streets (in that histogram bin) and its length represents the relative frequency of streets with those bearings. [...] Most cities' polar histograms similarly tend to cluster in at least a rough, approximate way. But then there are Boston and Charlotte. Unlike most American cities that have one or two primary street grids organizing city circulation, their streets are more evenly distributed in every direction. Boeing published a follow-up to the post to include to compare world cities.

Comments

DUH? this is Geography 101

[goombah99]

I recall this being taught in my middle school aerial cartography section of Geography. There's different epochs and influences on city layout. The french and spanish tended to build layouts conformal to landscape features like rivers, foothills, and drainages. The spanish ones always were oriented around a major zocolo plaza with the church at one end. Later American cities were Rectilinear grids. For an extreme case look at Salt Lake city which is paced out by distance from the church at the center.

But this is all well known, the design of cities and it's traceability to the varied possible influences used to be well taught

Re:Pretty interesting

[SharpFang]

Many older cities, especially in Europe, followed a circular diagram, with ray streets outwards and round ones connecting them. At first that would be the result of being squeezed into city walls, then followed expansion outwards, along these streets and filling in the space in between.

And cities located in hilly/mountainous terrain will have streets following curvature of the hills; the steep streets of San Francisco that completely ignore the slopes and make for such iconic scenes in car chase movies are something rarely seen in the world. Usually, you'll have streets that run along the slope, maintaining level or moderate climb/descent, and connecting/branching where terrain allows.

Re:You can probably guess Age

[Sique]

Not necessarily. Bejing for instance is pretty old, but very North-South/East-West oriented. The rectangular grid was laid out in the 13th century under the rule of Kublai Khan. With Madrid or London, you have a grid of large streets running North-South and East-West, and then lots of small streets in all directions. Rome has the famous seven hills and the Tiber river, which dominate the grid, and thus the streets go in every direction.

What you can see is the difference between a town developing out of an agglomeration of houses and settlements, and a planned community. Many U.S. cities fall in the later category, but so do Roman colonias from 2000 years ago, Middle Age towns in Central Europe or large Asian cities. If cities grow, it may even happen that a rectangular grid downtown loses its dominance in the suburbs, as they are former separate towns and villages merged with the larger town, or that vice versa an old core of irregular streets gets surounded by large, planned suburban communities, which cause the North-South/East-West grid to dominate the statistics.

Re:Pretty interesting

[rickb928]

Actully, think of it this way; coastal cities were likely developed earlier, with some notable exceptions on the West Coast, and so while they are constrained by the shoreline, they also were developed before grid layouts were common or imposed by planning, IE NO planning. Boston being an excellent example, Beacon Hill being settled before there was a city there, and the roads more likely being livestock paths before they were even horse paths or wagon trails. Chicago has a grid pattern right up to much of Lake Michigan, though Evanston shows some irregular streets. Los Angeles has a great mix of grid and non-grid, and I wonder if that can be traced to the time of development...

Phoenix is a grid, probably because it had planning from early on, while San Diego is quite a mess, probably because it lacked planning.

I'ts not just the coastline, it's also the age when the development occurred. In another area of interest, London is not so populated with skyscrapers as New York, probably because elevators did not exist when London expanded, while New York had elevators, and that enables higher buildings.

Planning enables streets to be laid out on grid. Coastlines do interfere with that, but coastal cities were settled earlier, before planning was an option.

Re: Pretty interesting

[Dragonslicer]

Here is a nice animation sequence showing all of the Boston landfill projects.