Eli5: it’s said that creating larger highways doesn’t increase traffic flow because people who weren’t using it before will start. But isn’t that still a net gain?

Question

If people are being diverted from side streets to the highway because the highway is now wider, then that means side streets are cleared up. Not to mention the people who were taking side streets can now enjoy a quicker commute on the highway

In: Engineering

Answer 1

A wider highway increases capacity but not traffic flow. Think of getting a wider hose (the highway), but using the same size nozzle (the exits).

Traffic flow is mainly dealt with by adding more alternative paths to destinations and alternative transit.