From top left—Rome, Portland, Sacramento, Paris, DC, and Dubai visualized through Boeing's open source tool. Geoff Boeing/OSMnx

A new open-source tool lets users compare the structure of cities around the world.

A city’s street network is like its skeleton—a foundation for features like pipes, electrical lines, buildings, and public spaces. The angles at which pathways intersect, the shapes they wrap around, and how wide or narrow they are convey how the city has evolved, and whether it’s designed to bring people together or fling communities apart. In that way, each city’s very identity lies in its streets.

The centrality of street networks to urban life was the subject of the 1993 book Great Streets by urbanist Allan Jacobs. In it, Jacobs includes maps, drawn in a style made famous by Italian architect Giambattista Nolli, to help illustrate the differences between good and bad urban matrices.

Now, Geoff Boeing, an urban planning scholar at the University of California, Berkeley, has taken a page out of Jacobs’s book and put it on the internet. As part of his dissertation, Boeing has developed a coding tool that draws from OpenStreetMap and visualizes any city’s street network to scale as a black-and-white, Nolli-esque map.

Boeing’s tool complements existing urban-design techniques. “Very often, this kind of computational urban data science speaks past urban designers—it’s unfortunate,” Boeing says. “A tool like this can help support urban designers in the questions they’re already asking. Basically, it streamlines the process [of analyzing urban form] and makes it reproducible without having to reinvent the wheel every time.”

In a blog post, Boeing explains how with just one line of code, users can open a square-mile window into any part of a city. (Be warned: Basic coding skills may be required.) Each resulting map is like an x-ray of the city it represents, allowing viewers to focus on the layout of the streets in the area they’ve selected (by inputting an address or coordinates). Here are a few examples:

These maps show which cities are older (Tunis and Rome, for example) and have evolved organically, and sometimes haphazardly, over time. In the planned cities, it’s easy to identify the decisions that shaped them. (In Paris, for example, you can spot the legacy of Georges-Eugène Haussmann’s 19th-century reconstruction.) It’s also clear from the maps how walkable cities, like Rome, pack much more life into one square mile than car-centric ones, like Irvine. But even in dense cities, border vacuums can be a disruptive presence. Check out the how Interstate 405 divides Portland.

Of course, Boeing’s maps don’t say much about what the actual pedestrian experience in these cities is like—whether the sidewalks are wide and shady, or parking lots well-oriented. But they provide enough information to get a sense of what a city is about. “You can really easily get a feel for the city’s traits and textures, whether it’s fine-grained or coarse-grained, and how it’s configured,” Boeing says.

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