Can building more roads make traffic worse? Here’s the mathematics behind it
A basic traffic model illustrates why adding road space does not always ease congestion. It considers 4,000 commuters travelling between the same starting point and destination, with two existing routes.
In the model, some roads have fixed travel times, while others get slower as more cars use them. With no other option, drivers split evenly between the two routes, and each journey takes 70 minutes.
The city then adds a short one-way link between points on the existing routes. This creates a third possible path, including one that uses the new link.
Drivers choose the route that suits their own journey time, rather than coordinating to reduce delays for everyone. The article sets up this change to examine how individual choices can affect the whole network.
Key points
- With the original road layout, 2,000 commuters use each route.
- At that split, both routes take 70 minutes.
- A new link gives commuters another route, but choices are made individually.