>>1963951>cars just "materialize" out of nowhere (they don't)More people drive because highways are prioritized to make them the most attractive option. This is essentially what induced demand means. This goes hand-in-hand with an urban area's growth.
>expanding highways is useless (it isn't)Expanding highways is useless. The reason it doesn't alleviate traffic is because no matter if you have a 6 lane or a 12 lane highway, the point of a highway or a train is to take people to where they need to go. Expanding the highway does not solve the bottleneck of the exits into the city where people are trying to go. This, along with basic geometry, is why highways don't scale well. A new lane on the highway adds capacity for another 1800-2400 cars per hour. My local subway's 8 car trains seat around 550 people each without accounting for standing room, meaning at it's current 20 minute intervals it exceeds the capacity of an extra lane. It takes less than a minute for a full train to empty downtown, whereas traffic always jams at the downtown highway exits. The system used to run at 10 minute intervals before budget cuts, and is capable of running more frequently than that.
>that reducing highway capacity will make traffic disappear (it won't)As long as there are alternatives, like the aforementioned subway, reducing highway capacity will actually reduce traffic. People mode shift to what they deem to be the more attractive option, in this case going to the suburban park and rides to take the subway downtown.
>refusing to expand roadways will stem sprawl (not happening)This is the only point you're even partially correct on. Single-family zoning does have a major effect on enabling sprawl, but even then, when you design around cars and expect everyone to drive everywhere they want to go, the car infrastructure (parking, highway interchanges, etc) make everything much farther apart than it needs to be, thereby making the area unwalkable and less attractive for biking
