The congestion paradox

Traffic is so bad, why don’t we build more roads to deal with it? Since the 1940s, city planners have known (and often ignored) one counterintuitive rule: more roads means more congestion.

Let’s talk about Robert Moses. He basically made New York what it is today – from the 1920s to the 1960s he held a range of powerful roles in planning commissions, bridge and tunnel authorities, parks departments, and the governor’s office.  Through these roles he was responsible for the creation of the Triborough Bridge, the Brooklyn-Battery Link, Interstate 278, the Cross Bronx Expressway, and many other roads. He was also the one who won the UN Headquarters for New York and was at least partly responsible for the Dodgers and Giants baseball teams moving out west.

But! It’s the road-building that I’m writing about today. Moses built many bridges and roads with the goal of alleviating congestion in New York. However, every time a new bridge was built, traffic did not improve. Instead, people who normally wouldn’t drive switched from public transport to cars. People who wouldn’t normally make the trip decided that now it was worth it. More roads = more traffic.

Now, the fact that people were observing this back in the 1940s doesn’t change the fact that people keep insisting that more roads will solve traffic problems. And I understand why: it makes intuitive sense. It’s just mostly wrong. The technical term for this is “induced demand” – as in, by building roads you’re inducing more demand for roads.

One final fun fact: Robert Moses didn’t have a driver’s licence.

• Induced demand
• Robert Moses