Closing some streets in a city decreases travel time

The Christian Science Monitor's Bright Green Blog presents an interesting bit of information: strategically closing certain streets in a city can actually improve travel time of drivers.

The context here is that providing for more walkable and bicycleable cities is usually portrayed as a venture that is at odds with the interests of the motor vehicle-driving public. But it turns out that in many cases they are not. Closing certain streets to through traffic, making traffic flow slower but more smoothly, and changing the way intersections are handled can make a city much more inviting for walking and bicycling--while simultaneously decreasing motor vehicle travel times and improving roadway safety for all users.

The benefits are much the same as with another solution we've often mentioned here on MoBikeFed News--the "Road Diet".

Here is what the Bright Green Blog has to say:

File this one under "intensely counterintuitive." A recent study has found that closing off certain streets can actually relieve traffic congestion. . . .

The authors compared the Nash equilibrium time to the socially optimal travel time, and dubbed the ratio between the two “the price of anarchy.” In their study of the Boston area, which looked at travel times from Harvard Square to Boston Common, the price of anarchy at peak traffic times made for a journey that is 30 percent longer.

But the price of anarchy drops if you close a few roads, because individual drivers are less able to selfishly optimize their routes. In their analysis, the authors identified six streets in Boston and Cambridge: By closing those streets, they say, the optimal collective travel time would decrease between the two points.

At first blush, this study seems dissonant with findings that traffic flows can be improved by increasing vehicular anarchy. As I noted a few months back, there is considerable evidence that removing all traffic controls – lights, signs, road markings, and even the distinction between streets and sidewalks – can actually make traffic move more smoothly, as well as cut down on the number of accidents and increase the area’s economic vitality. The idea behind these “shared streets,” which have been successfully deployed in many European cities, is that the lack of traffic signs makes you take personal responsibility for directly negotiating with the pedestrians, cyclists, and other cars around you, instead of, say, gunning it through an intersection just because you know you have the light.

But maybe these two traffic models have more in common than it first seems. Both encourage individuals to drive more slowly so that everyone gets to his destinations faster. Both favor a holistic approach to traffic, one that designs from the perspective of the overall flow rather than that of an individual driver. And both open up more space for pedestrians.

It’s not too difficult to imagine a city designed with these principles in mind. Fewer roads with slower but smoother traffic. Spaces that can easily be converted to car-free zones to suit the needs of the network. And fewer opportunities for people to drive like jerks. Sounds like a nice place to take a walk, actually.