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

The infrastructure currently being built directs future growth.

If a highway is built then factories and big box stores build as close to it as possible. Then houses get built outside of town that require longer drives. Ending up with a line with housing development on the outside, then mixed factories/large shopping centers, then the old city center. The parts of town not near the highway become less desirable and begin to decay.

If a grid of mixed smaller residential and commercial roads are built then a town ends up with a more distributed commercial district with factories and big box stores moving to the edge of town. This spreads the traffic load out among many smaller streets.

Ultimately using highways to reduce commuting time fails as it concentrates the traffic, creates dangerous bottlenecks at exits and pulls the population further away from their destinations creating more driving.