We fill roads in cities because the population wants/needs to travel. If we would instead build trains those would fill instead. Trains are a lot more cost effective in cities, but no city (not even transit cities like Paris) builds enough of them to make trains a better alternative than cars.

Note that by the time anyone realizes roads are full and they need "one more lane" the road has 6 times more cars on it than it can safely handle - people just give up their safe following distance. One more reason to build trains.

The moment you introduce tolls onto major roads, often they don't meet financial projections, have to be bailed out, etc.

That's only when new roads satisfy pre-existing demand.

The fact that someone can't do something doesn't imply that they don't want to do it.