* Illustration: Martin Woodtli * Our nation is gridlocked. Congested roadways mean that each year, the typical US commuter spends about 40 hours in traffic. That adds up to $78 billion in lost time and wasted fuel, not to mention environmental damage, road rage, and the proliferation of lame drive-time shock jocks. What's worse, most jams aren't the result of an accident or a breakdown; they have no clear cause at all. Drivers react to other drivers, and those drivers react in response. A tiny hiccup in traffic — you're fiddling with the radio and get a little too close to the car in front, so you hit the brakes — can send a tremor rippling upstream for miles. One Japanese scientist found that in moderate traffic, a single erratic vehicle can trigger feedback effects that push the entire system into a new equilibrium: a standstill.
The reflexive response to congestion is to add more road capacity. But that, alas, is self-defeating. As the history of cities like New York and Los Angeles shows, a new bridge or expanded artery just invites more people to drive. In the long run, it alters decisions about where to live and work — highways create suburbs, not the other way around. Pent-up demand around major US cities is so great, urban planners say, no amount of construction would alleviate gridlock. Singapore, London, and Stockholm have tackled rush hour problems with "congestion pricing" schemes that use heavy fees to encourage people to share rides or limit downtown trips to off-peak hours. Can the US hop on the same bus? A similar proposal for New York City has stalled.
