Saturday, January 10, 2009

Birds of a Feather

Which would be safer? An intersection with traffic lights, crosswalks and lane markings? Or a large plaza where people on foot, in cars, riding bicycles—even some in wheelchairs—navigate the space however they can manage? Most people would guess traffic controls and street markings would make an intersection safer, but, surprisingly, the opposite turns out to be true.

And the reason has a lot to do with birds.

Consider the Laweiplein intersection. Traffic engineers have flocked to this plaza in Holland for years, amazed at the sight of people moving through the space without any of the usual traffic controls. Like roads. Or even sidewalks. You can watch videos of the place here.

The scene can look quite chaotic at first—cars, trucks, pedestrians, all traversing the space in a seemingly random fashion, moving first this way, then that, to make it past one another. They avoid collisions the old-fashioned way: by looking at each other. And they do it, incredibly, in half the time it usually takes to get through an intersection of this size.

The Dutch intersection, designed by the late Hans Monderman, was one of the first demonstration projects of the shared-space approach to traffic engineering. This counter-intuitive idea has been remarkably successful, cutting not only travel time but also accidents. An intersection in the town of Haren in the Netherlands, for example, saw accidents drop by 95%—from 200 a year to about 10—after being redesigned as shared space.

Shared space ideas began to spread across Europe after the completion of the Laweiplein intersection in 2001. In 2003, the European Union launched a research project on shared space that brought swarms of government traffic officials to Drachten to see how the idea worked. Soon, shared space streets were popping up in countries across Europe.

The town of Bohmte in Germany was one of seven pilot projects launched by the European Union study—other locations in Holland, Belgium, Denmark and the UK also participated. In Bohmte, two traffic rules remain: a speed limit of 30 mph is imposed and everyone—car, pedestrian, bicyclist—must move to the right of everyone else. Traffic accidents in the town have fallen from an annual average of 50 to zero in just one year.

Similarly, on busy Kensington High Street in London where crossings and railings have been removed, accidents have dropped an astounding 44% since the changes were made two years ago, according to Ben Hamilton-Baillie, the UK’s primary shared-space advocate.

How does it work? The shared space philosophy, so different from that which governs traffic policy in the US, is based on the concept of self-organization. When a crowd of people are subject to the laws of self-organization rather than to traffic laws, they behave like a flock of birds or school of fish.

This doesn’t mean there is no order, however. When birds flock, no one bird is in charge, yet the group moves in an orderly fashion. The flock functions as it does because each bird senses the position and direction of motion of its neighbors and adjusts its own flight to match. The result is a smooth, even dance-like, movement of the flock. You can click here to watch an amazing video of birds flocking in Rome, showing just how orderly—and beautiful—self-organization can be.

Shared-spacers are quick to point out that the approach works only at low levels of traffic. Get too many people in one place and the whole thing breaks down. This can be true even if there are no cars, as can be seen in the cases of tragic stampedes that break out in situations where too many people are trying to move through too small of a space.

Norman Garrick, Director of the Center for Transportation and Urban Planning at the University of Connecticut, explains that shared space is based on the premise that design controls behavior. Signs, signals and street markings play a subordinate role to the physical layout of the space.

Although the shared-space approach has influenced traffic planning in hundreds of European cities, the idea has only just begun to appear in the US. Garrick explains that the idea of shared streets has been slow to catch on in the US because it challenges prevailing orthodoxy about how streets should be designed. “The idea of regulating traffic and separating users in time or space is very ingrained in our design philosophy,” Garrick explained in a recent paper.

The city of Cambridge, Massachusetts, for example, recently converted Winthrop Street in Harvard Square into a shared space and Santa Monica and Portland, Oregon are incorporating shared space ideas in more pedestrian-friendly approaches to street design.

The philosophy behind the shared space movement requires a strong shift in belief —away from regulation and control. It also requires a belief that people are capable of organizing themselves —and can be trusted to be at least as orderly as a flock of birds.


  1. Arusha, Tanzania, where Emily lives is a city of over 600,000 people which recently got its first traffic signal at a major intersection.
    There's a transporation movement called "complete Streets" in the US, but I don't know if it's incorporated shared space concepts yet.

  2. Thanks for your comment, Mary Martha! I've not heard of the 'complete streets' movement, but it sounds interesting - I'll look it up. Thanks for the tip! And thanks for stopping by.