I have long thought, particularly when stuck in traffic, that the Federal Highway Act of 1956 AKA the Interstate Highway Defense Act might have been counter-productive. As it turns out, I may have been right:
As a kid, I used to ask my parents why they couldn’t just build more lanes on the freeway. Maybe transform them all into double-decker highways with cars zooming on the upper and lower levels. Except, as it turns out, that wouldn’t work. Because if there’s anything that traffic engineers have discovered in the last few decades it’s that you can’t build your way out of congestion. It’s the roads themselves that cause traffic.
The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more. Though some traffic engineers made note of this phenomenon at least as early as the 1960s, it is only in recent years that social scientists have collected enough data to show how this happens pretty much every time we build new roads. These findings imply that the ways we traditionally go about trying to mitigate jams are essentially fruitless, and that we’d all be spending a lot less time in traffic if we could just be a little more rational.
The point seems to be that marginal increases in the number and size of roads, slowly and over time, changes habits and preferences in such a way as to produce more traffic. The alternatives suggested include enormous over-capacity (a “100 lane highway”) or some sort of disincentive scheme like congestion pricing or raising parking fees.