“You Don’t Build a Church for Easter Sunday”
What is the obvious solution to traffic congestion? “Build more roads!”  “But more roads bring more traffic!” “Then build even more roads!”
Tom Vanderbilt’s new book, Traffic: Why We Drive the Way We Do (and What It Says About Us), is a highly readable examination of some very interesting and significant statistical and behavioral data about driving, traffic and safety.  In Chapter Six, “Why More Roads Lead to More Traffic (and What to Do About It)”, Vanderbilt explains why more roads create more traffic: when new lanes are added to a highway, congestion drops, encouraging more drivers onto the highway, which creates more traffic, resulting in congestion possibly even higher than before.

Vanderbilt tells the story of I-710 in southern California.  A labor dispute at the ports of Long Beach and Los Angeles kept nine thousand trucks off the interstate for several days.  As though sucked into a vacuum, other drivers, learning that the road was now uncongested, took to the route, filling in the void left by the trucks.  But the highway authority did not notice a similar drop in traffic on parallel roads – the drivers seems to have “materialized out of nowhere” to take advantage of the opportunity provided by nine thousand fewer trucks.  When the labor dispute ended and the trucks returned to the road, traffic was worse than ever and the new cars left 710.

In an interview on Amazon.com Vanderbilt talked about suggestions for making roads safer and traffic less maddening.  Here is a snippet:

“We can’t build our way out of traffic, but we can think our way out. Building more roads when they’re already under-funded doesn’t seem workable, and given that most roads are only congested part of the time, it’s not really the most efficient solution anyway, for loads of reasons. As a former Disney engineer told me when I asked why they didn’t just build more rides instead of worrying about new ways to manage the long queues, ‘you don’t build a church for Easter Sunday’.”

When it comes to managing traffic, there are numerous technological, economic, sociological and psychological solutions that are already working on highways and in cities – from feedback sensors that detect traffic jams and reroute cars, to traffic lights that adapt to changing demand – or no traffic lights at all, roundabouts in place of intersections, and traffic calming techniques such as roadside plantings and changes in pavement color and texture.

The message here is that as we examine the state of our transportation infrastructure and plan for its future, we should be careful of the assumptions we make about highways, traffic congestion, and the drivers whose behaviors are at the heart of the matter.

Listen to an interview with Tom Vanderbilt on NPR.