I just finished Tom Vanderbilt’s Traffic: Why we drive the way we do (and what it says about us).  As a book, it’s a bit clumsy, like its title.  But he’s got a fascinating subject.  Traffic– or driving, really– turns out to have a lot of paradoxes.

  • The average driver is lousy but thinks he’s great.  This is largely due to the reversed feedback: bad driving is actually positively reinforced by the long stretches where it doesn’t cause an accident.  Normally we’re not even aware of the near-misses that our bad habits produce.
  • Slower is faster.  Past a certain level of congestion, you get more cars getting through by people driving steadily, not as fast as they can.  E.g. in an experiment, police limited the number of cars that could enter the Holland Tunnel in NYC to 22 per minute.  The result: throughput rose from 1176 to 1320 vehicles per hour.
  • Safer is more dangerous.  Remove obvious obstacles, give plenty of space, and make a road look like a highway, and people drive like it’s a highway… and if it’s not, if it’s a city street, this causes accidents.  A slight level of confusion is good for us: we slow down, stay alert, notice the pedestrians and bicyclists (and because slower is faster, gridlock is avoided).
  • Adding more roads creates more traffic; adding more parking adds more congestion. 

There’s also a neat example of what we might call the paradox of liberalism: solve a problem, and people forget what the problem was and begin to resent the solution.  In Minneapolis, a state senator (Republican, naturally) got a moratorium on ramp metering (restricting the number of cars that could enter at a given ramp).  After all, the traffic on the highway is moving, why can’t we join it?  Results: speeds dropped and travel time went up; in certain areas highway throughput halved.  The meters were reinstated.  The traffic was moving because you couldn’t just rush into it.

It’s hard to finish the book without thinking that designing our lifestyle around the automobile was probably kind of a bad move (and that’s without getting into global warming or running out of oil).  Also that flying cars would probably be exponentially more complicated…

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