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 issue is that, in addition to the induced demand problem, increasing a highway inside a city or metro area, just takes the money away from other areas, such as busses, trains, metros, and other forms of people movement that aren’t cars.

Not to mention getting people across a highway is exponentially harder and more expensive, the more lanes it has. Either you build a bridge over it, which becomes more expensive the longer the span is (you’re not going to drop a support mid freeway), or you build the freeway over a tunnel/on a bridge span itself, which suffers the same problem.

In an ideal world, people have the option to drive. Some people just need to, like tradesman, people who’s jobs require driving to homes that may be outside the general metro area. But the general commute, is done through public or personal transit.

If you’re interested, look up the 15 minute city design (FMC/15mC). It’s the principal that basically means you don’t *need* to drive your kids to school, you don’t *need* to drive to Walmart to do the weekly shop, and even if you have parking, it’s not on-street/above ground, so it’s not taking up useful space.
It also makes use of mixed use zoning, like an apartment block with commercial on the ground floor, maybe a gym on the 1st, as that’s not a necessary ground development, and parks/green space instead of parking lots, to allow the residents and those around them to use it, instead of just those interested in accessing that plot.