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Monday, Nov 23, 2009
There's another step in the second-generation logic process. Safety analysts have known for several decades that the maximum vehicle speed at which pedestrians can escape severe injury upon impact is just under 20 miles per hour. Research also suggests that an individual's ability to interact and retain eye contact with other human beings diminishes rapidly at speeds greater than 20 miles per hour. One theory behind this magic bullet, says Hamilton-Baillie, is that 20 mph is the "maximum theoretical running speed" for human beings. (Evolutionary biologist E.O. Wilson has drawn similar conclusions.) "This is of interest," he says, "because it suggests that our physiology and psychology has evolved based around the potential maximum impact on the speed of human beings."
The ramifications go beyond safety, says Hamilton-Baillie, to bear directly on the interplay between speed, traffic controls and vehicle capacity. Evidence from countries and cities that have introduced a design speed of 30 kilometers per hour (about 18.5 mph) -- as many of the European Union nations are doing -- shows that slower speeds improve traffic flow and reduce congestion.
"This surprises many people, although mathematically it's not surprising," Hamilton-Baillie says. "The reason for this is that your speed of journey, the ability of traffic to move smoothly through the built environment, depends on performance of your intersections, not on your speed of flow between intersections." And intersections, he says, work much more efficiently at lower speeds. "At 30 miles per hour, you frequently need control systems like traffic signals, which themselves mean that the intersection is not in use for significant periods of time. Whereas at slower speeds vehicles can move much more closely together and drivers can use eye contact to engage and make decisions. So you get much higher capacity."
Combining slower speeds with a reduction in traffic controls, in other words, may have more than public safety and shared-space benefits. It also appears to profit the driver. (This is the logic behind the modern roundabout, a redesigned version of the classic traffic circle that is replacing signalized intersections in the United Kingdom and is gaining acceptance among transportation officials in the United States).
"You can see this is the way to break out of the pro-car, anti-car debate," Hamilton-Baillie says. "Because the shared approach very much accepts the car as a vital useful component in cities that will remain with us for some generations to come."
Let's return to China for a minute. If traffic in the world's most populous country provides a useful comparison and contrast, it's because second-generation traffic calming isn't about anarchy; it's about studied anarchy. In essence, Hamilton-Baillie is advocating for a new field: one that blends traffic engineering with urban design. Or, as he titled an upcoming paper: "Urban Design: Why Don't We Do It in the Road?" There's a place for highways and roads dedicated solely to the movement of automobiles, he says. Just not in the city, where streets constitute 70 percent of all public space.
"You have to have a completely different approach to the design of streets in the broad urban realm," he says. "You have to make an absolutely clear transition between those roads that are necessary, the state-controlled and legislative world of the traffic environment, to the human-controlled, culturally controlled world of the city, where you pick up your rules not from what you're allowed to do, but from a much more subtle and complex series of codes that are implicit through design and environment."
"If I walk into your living room, I do not need a sign that says, Do Not Spit on the Floor," he explains. "Indeed, if there were such a sign, it would probably be counterproductive."
Over the last few years, the shared-street concept has emigrated out of mainland Europe to the United Kingdom. In addition to home zones, which are cropping up in isolated residential developments, the city of Manchester is currently reconfiguring a major section of its central core according to shared-space principles. Hamilton-Baillie himself is working a project that he says is the first in the country to bring together all the elements of second-generation traffic calming: removing the road markings from a road that runs past a primary school in the city of Bath. It's a project, he says, that capitalizes on the area's "rich urban morphology" -- St. James Square, the school and a historic church -- to "create a series of places rather than a single highway."
In the United States, as one might expect, policymakers haven't exactly embraced the virtues of ambiguity and uncertainty embodied in second-generation principles. "Woonerfs are certainly being planned on private property," says James Daisa, a project manager at Kimley-Horn Associates and a national expert on pedestrian-friendly development. "But the concept has yet to come to bear on public streets." City codes are part of the problem, he says. The reluctance of traffic engineers is another.
Consider the case of Brookline, Mass., which installed a woonerf in front of a Marriott Hotel last January. A patchwork of brick pavings, the shared-space lacks big curbs, and the sidewalk and street are all at the same level. But as reporter Anthony Flint noted in the Boston Globe, the public works department botched the entire concept by painting white lines and big right-turn arrows on the street, and placing yellow-and-black-striped rectangles on the landscaped "bump-outs."
"It's clear that advocates and private developers aren't sufficient to bring about a true woonerf," wrote Flint. "The traffic engineers need to be in the room, and they need to understand the concept. A fact-finding trip to the Netherlands may be in order."
For their part, many American traffic engineers say one critical ingredient is missing for a system built around shared spaces to work in the United States: a communal sensibility. "We live in a culture that gives so much value to the individual and the expression of that is how we act in a car," says Robert Burchfield, a city traffic engineer in my home town of Portland, Ore., which is nationally recognized for its preservation of public space and its dedicated network of cycling lanes and pedestrian pathways. "I'm not comfortable with less order when I can't get people to go below 50 or 60 miles per hour."
But this, of course, is precisely the point; redesign the street environment as an active community space, and you equalize the power relationship between cars and human beings "The real gain in urban quality does not come from clawing back areas of the city from cars, as important as that is," said Hamilton-Baillie, who gave a talk at the Portland Department of Transportation last fall. "But the next step is how you apply a broader approach to those areas where you need cars and trucks, bicycles and shops, and pedestrians and children's play, all those different functions to take place in precious urban space."
Even if we're not ready to send our children merrily into the street, many of us, intuitively, have already embraced the concepts behind second-generation traffic calming. Like most other parents, I've drilled into my kids the fact that traffic lights and signs work for cars, but don't necessarily serve pedestrians who want to make it across the street in one piece. "Look left, look right, look left again," I preach ad nauseum -- even when the walk signal is green. And who can resist the symbolism associated with recapturing the street for the (teeming) masses? It's not quite the fall of the Berlin Wall, but the shared-space approach overturns the landmarks of sedentary isolation -- everything from gated communities to skyrocketing childhood obesity rates -- to celebrate the complexity and contradictions of city life.
The absence of traffic controls means that people are out for themselves; the trick is, they have to look out for everyone else as well. Second-generation traffic design is a curious mix of selfishness and altruism, of order amid chaos. And, after a fashion, it just might work.
