Urban planning around the world seems to have become obsessed with the idea of creating gated communities and disconnected street networks. This is extremely bad news for people who like to walk and for the environment. Urban sprawl and disconnected streets create barriers to and discourage walking. Cul de sacs and gated communities make it very difficult to make journeys without a car. They therefore lead to an increased use of vehicles and CO2 emissions. On the other hand connected street networks encourage walking and the use of public transport.
Researchers from the McGill University in Canada and the University of California have devised a way of measuring urban sprawl around the world. The Street-Network Disconnectedness index (SNDi) measures street connectivity. The SNDi uses OpenStreetMap data to work out an urban sprawl score for street networks across the world. This score is calculated by looking at such as factors as the number of routes possible between locations on a street network, the number of dead ends, and the distance of possible travel between locations.
The Sprawl Map allows you to explore the SNDi given to towns and cities around the globe. Zoom-in on any town in the world and you can see the SNDi scores given to individual roads. On the map streets are colored to show how well connected they are. Poorly connected streets, such as cul-de-sacs or loops, where people are forced to drive, are colored red. Well-connected streets, where walking is easy, are colored blue. Zoom out and the Sprawl Map provides a choropleth view, which shows how connected different countries, regions and cities are overall.
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