Ravings of a raconteur and randonneur

Congestion isn’t solved by more roads

by Jimmy on 9 Sep ’15, no comments

New roads don’t fix traffic. In fact, they often make it worse. This has not only been observed in many real-life cases, but, as the mathematician Josefina Alvarez pointed out recently in Plus magazine, it’s also a mathematical reality. In 1968, maths thinker Dietrich Braess even proved this: “an extension of a road network by an additional road can cause a redistribution of the flow in such a way that the travel time increases.” It’s called the Braess paradox, and has implications well beyond roads.

The maths that show how less roads lead to less traffic