Skip to content.

News and commentary from the world of biking and walking.

Braess’s paradox: why traffic seems to always get worse

If you’ve ever wondered why our overall traffic congestion never improves, no matter how many new roads we build, then the answer is Braess’s paradox. It states that adding more roads to a network can actually slow down traffic. That may seem counter-intuitive, but we can plainly see it happen in all of our modern towns.

One thing about Braess’s paradox is that it’s not simply observational. It’s based on mathematics. Like all paradoxes, it only seems counter-intuitive on the surface, but it’s actually logically sound. In fact, we have formulas for calculating exactly how the paradox works. (Wikipedia has a wealth of explanation.)

Since the paradox was first discovered in 1968, the real mystery now is why do we keep ignoring it. Towns across North America keep trying to improve traffic by adding new car lanes, and we act surprised when congestion keeps getting worse. Our expanding roads tear neighborhoods apart, pollute our communities, kill more and more road users, and make biking and walking close to impossible. On top of that, they don’t even fix the problem we built them to solve.

The existence of Braess’s paradox isn’t controversial, but its application is. Expanding roads today is entangled with emotions and politics. But our society’s love affair with car infrastructure will have to end sooner or later, since the status quo is unsustainable. Accepting the reality will have to be the first step.