Can building more roads make traffic worse? Here’s the mathematics behind it

Tackling traffic congestion is one of the biggest challenges facing large cities around the world. When it comes to reducing congestion, one solution almost instinctively comes to mind: build more roads or widen existing ones.

But the science of transport economics has shown for decades that increasing road capacity does not necessarily translate into smoother traffic. In fact, under certain conditions, it can do the opposite.

Here’s how it works.

A simple road network

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© La Conversation - dimanche 11 octobre 2026