[1] https://www.wired.com/story/the-us-wants-to-close-the-suv-lo...
If lanes are smaller, then people buy smaller cars. If parking spaces for compact cars are differently priced than that for huge cars, then people buy smaller cars. Set insurance minimums for liability by vehicle class. (scale it to liability damage statistics)
There are a lot of ways to strongly disincentivize big vehicles. If we merely start making them pay for the space they occupy, they immediately become too expensive.
Of course that will never happen so you're right...
They just leave the middle flat so vehicles that don't fit (and people who can't be bothered to go around) can drive on it.
Can't fix crap drivers, no matter how hard we try.
A roundabout that is elevated and can't be driven over does actually change behavior. Average driver behavior is actually something we can improve!
Changing driver behaviour though? I'm pretty negative about it.
I get honked at regularly for stopping at those stop signs. The police head to Twitter and make fun of a few drivers a week for stunt driving. The city is opening a new processing centre because they can't handle the load of the speeding tickets from the speed cameras.
Yet I only see more and more aggression out there. People drive like they're the only ones on the road.
It's a 40 minute walk, one way, from my door to the nearest store. As much as I'd love to avoid the situation altogether, I don't have time to walk. Forcing people to drive everywhere is probably part of the problem, though.