Eric Jaffe provides a reminder that traffic is not lessened if there were just wider roads:

“Wider Roads = Less Traffic”—The most enduring popular traffic myth holds that building more roads always leads to less congestion. This belief is a perfectly logical one: if there are 100 cars packed into one highway lane, then building a second should mean there’s 50 cars in each. The problem, as transportation researchers have found again and again, is that when this new lane gets added the number of cars doesn’t stay the same. On the contrary, people who stopped driving out of frustration with traffic now attack the road with an enthusiasm unknown to mankind.

While residents of heavily congested metro areas have a suite of four-letter words to describe this effect, experts call it “induced demand.” What this means, simply put, is that building more road eventually (if not always immediately) leads to more traffic, not less. Fortunately, local leaders are starting to distinguish reality from myth when it comes to induced demand. Unfortunately, the best way to address it—congestion pricing—remains all-but politically impossible in the U.S. That pretty much leaves one thing to do: deal with it.

A congestion tax is one way to deal with the issue: make people think twice about driving into heavily trafficked areas. At the same time, broader solutions could be employed: planning communities and regions that don’t rely so much on solo driver trips (such as through denser development); increasing funding to mass transit and providing more regular service and/or more options; and finding other ways to cut incentives on driving such as increasing gasoline taxes or paying per mile for driving. Of course, these broader approaches may be asking too much as Americans still like the option of driving. But, it may take some bold politicians and municipalities to try congestion pricing and show that it can work before it is widely adopted.

In other words, you may be able to show studies that demonstrate how this myth isn’t true but perhaps Americans dislike the truth – and the solutions that go with – even more.