A Fantastically Clear, Concise Explanation of Why Traffic Happens
Eric Jaffe | The Atlantic Cities | September 20, 2013 | link
Tom Vanderbilt, author of Traffic, gave a great 20-minute overview on the counterintuitive science of congestion at the Boing Boing: Ingenuity conference in San Francisco last month. Turns out a lot of the problems we ascribe to poor roads or other drivers are really our own fault. “[T]he individual driver cannot often understand the larger traffic system,” says Vanderbilt.
The talk is worth a full watch — especially if you’re parked in gridlock — but we’ve plucked out a few nuggets most relevant to metro area commuters.
Executing the “zipper” merge. Road work often reduces two lanes of traffic down to one. In these situations, American drivers typically merge into the right lane as soon as possible and form one long line. The main reason they do this is because people think it’s bad behavior to stay in the left lane and merge late.
In fact, says Vanderbilt, traffic would be much better off if cars stayed in both lanes then merged at the very end, one by one, like a zipper. It’s safer (fewer lane changes), it reduces back-ups (often up to 40 percent), and it quenches road rage (still on the rise).
The zipper merge is used in Germany but can’t overcome its bad reputation in the United States. A trial in Minnesota failed because drivers wouldn’t stay to the left. They were too nice.
Maintaining a steady speed. A big reason for traffic is that too many cars are trying to occupy too little space on the road. But that’s not the only problem. A human inability to maintain a steady speed and following distance on the highway makes traffic a lot less smooth than it could be.
A few years back a group of Japanese physicists gathered drivers on a closed loop course and asked them to keep a certain speed and following distance. They couldn’t do it. After a while the system broke down and a reverse shockwave rippled back through the whole line of cars.