Worldchanging ally Francis Pisani turned us on to this Salon piece "Why don't we do it in the road?" about the entirely counter-intuitive finding that the best way to manage auto, bike and pedestrian traffic may be to mix them up: rip out the sidewalks, tear up the stopsigns, and let 'em have at -- the so-called "shared spaces" approach. Based on the Dutch "woonerf" street design, it seems to work:
"Reversing decades of conventional wisdom on traffic engineering, Hamilton-Baillie argues that the key to improving both safety and vehicular capacity is to remove traffic lights and other controls, such as stop signs and the white and yellow lines dividing streets into lanes. Without any clear right-of-way, he says, motorists are forced to slow down to safer speeds, make eye contact with pedestrians, cyclists and other drivers, and decide among themselves when it is safe to proceed. ...
"When it comes to reconfiguring streets as community spaces, ground zero is once again Holland and Denmark, where planners are removing traffic lights in some towns and cities, as well as white divider lines, sidewalks and speed limits. Research has shown that fatality rates at busy intersections, where two or three people were being killed every year, dropped to zero when controls and boundaries were taken away. (This is food for thought among alternative-transportation advocates in the United States, who extol northern Europe as a model precisely because so much space in these countries is dedicated to segregated pedestrian spaces and bike lanes.) ...
"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."
