A global study has analyzed the design of city streets to determine the best connected cities. Connectivity influences people’s decisions to drive or travel by foot, say authors of the first global analysis of street connectivity. The findings, writes New Scientist (12 December 2019), could be used by urban planners to design cities with lower climate impacts.
Christopher Barrington-Leigh at McGill University in Canada and Adam Millard-Ball at the University of California, Santa Cruz, assessed the connectivity of street networks in different cities by counting the numbers of intersections, streets radiating off each intersection, dead ends, and loops. They also measured the straightness of the routes between each intersection. They performed this analysis on all 46 million kilometres of the world’s mapped roads.
The results show that cities with grid-like street patterns have the best connectivity. Old European cities like Paris and Vienna also score well – despite their intersections tending to be irregularly spaced and three-way instead of four-way – because they still form highly connected networks.
Cities that have cul-de-sacs, crescents, and dead-ends are the least well-connected because their curvy, dead-end streets create disjointed suburban islands.
Since well-connected streets make it easier to walk, cycle, and access public transport, cities with greater street connectivity tend to have lower rates of car ownership and higher proportions of people walking to work.
This suggests that the way urban planners design urban spaces will have long-lasting impacts on the use of cars and their greenhouse gas emissions, because once streets are laid down, they are essentially “locked in,” says Barrington-Leigh. “The choice about street connectivity in new developments is one of the largest climate-relevant investments that humankind is making and yet it’s been grossly overlooked,” he says.
Overall, the amount of urban space across the world is set to triple between 2000 and 2030.
Effective street connectivity may also lower climate emissions because it makes it easier for people to come together and share resources, says Barrington-Leigh. “In contrast, if you live in cul-de-sac hell in the suburbs, it’s harder to get anywhere, so you might have a swimming pool in your backyard instead of going to the local public pool, or a home theatre in your basement instead of going to the cinema, or a large freezer because you can’t go shopping as often,” he says.
“Historically, street grids were idealised in Ancient Rome and China because they facilitated efficient transport of people and goods. Cul-de-sacs became popular in America and England in the 20th century when cars made it possible for people to spread out and planners thought they would create safe havens for kids to “play street hockey or run over to their neighbours,” says Barrington-Leigh.
Examples of Well-Connected Cities (Grid-like Street Patterns)
Adelaide, Alexandria, Berlin, Budapest, Buenos Aires, Hong Kong, Karachi, Khartoum, Madrid, Marrakech, Montreal, Osaka, Paris, Santiago, Seoul, St Petersburg, Taipei, Tokyo, and Vienna.
Examples of Mid-Range Connected Cities (Irregularly Spaced Streets)
Auckland, London, New York, and Sydney.
Examples of Poorly Connected Cities (Cul-de-Sacs, Crescents, Dead-Ends)
Accra, Bangkok, Belgrade, Cleveland, Gainesville, Guatemala City, Ho Chi Minh City, Houston, Los Angeles, Manchester, Manila, Raleigh, and Tijuana.
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| Adelaide (Well-Connected City) |
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| Bangkok (Poorly Connected City) |
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| Ho Chi Minh City (Poorly Connected City) |
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| Karachi (Well-Connected City) |
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| Karachi (Well-Connected City) |
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| Khartoum (Well-Connected City) |
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| London (Mid-Range Connected City) |
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| Madrid (Well-Connected City) |
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| Paris (Well-Connected City) |
Journal reference:PLoS One, DOI: 10.1371/journal.pone.0223078
MARTINA NICOLLS is an international aid and development consultant, and the author of: Similar But Different in the Animal Kingdom (2017), The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
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