Mobility explained: Braess' Paradox

I’m going to try to introduce different terms here to bring insights and knowledge for all Telraam Talks members. Some of these will be familiar to you, some may not. I hope we can all learn from them, and if you have more to add, PLEASE do add your thoughts in the discussion below.

Braess’ Paradox

Definition: Braess’s paradox is the observation that adding one or more roads to a road network can slow down overall traffic flow through it.



This is one of those wonderful things that, once you’ve got your head around it, change your perspective forever.

Braess’ Paradox is the phenomenon that can occur in transportation networks, such as roads or public transit systems. It states that adding a new road, a new lane or transit line to a network can actually increase traffic congestion, rather than reducing it. :exploding_head:

Why? or How?

This happens because the new road/lane/line/route creates a new travel option for drivers or commuters, attracting new users, which in turn leads to more traffic on all roads in the network.

Here’s a scenario:

A commuter is evaluating their options for their commute before leaving home, and if they think that there’s a new fast or empty road they can use, then why bother with any alternatives? So they drive.

But … so do all the other commuters, since they all know about this new road/lane/route.

So what happens? Congestion on the new road.

And since the new road probably also attracted drivers who did not drive before (because of the congestion), the total volume on all roads actually increases, until they are all congested enough that new drivers are turned away.

Final Result?

Even more cars end up on the road, so the congestion that the new road/lane/route was supposed to relieve is increased.

This can be a surprise for people who think that building more roads or transit lines will always improve traffic flow. The counter-intuitive way to reduce vehicle congestion may actually be to REDUCE the number of roads and lanes (and invest in making alternatives easier/cheaper/better), and make the original choice of driving a vehicle less attractive compared to the alternatives.

As a citizen scientist, you can monitor traffic in your street and observe the effect of a new road or lane, and contribute to the understanding of how transportation networks work.

For more information, check this great page out:


as far as I know, all countries call this after the German Mathematician Dietrich Braess, but if you know of alternative terms or names for this description, please let me know