Huh? If you limit supply, demand goes down?
Your logic would say that the solution to Los Angles traffic problems is to close half the lanes and wait for people to sell off their cars?
It works for cars, since there are acceptable alternatives (biking, walking, carpooling, Uber, etc). It works less well for housing, as leftist NIMBYs often advocate, since one alternative (homelessness) is very unappealing, and the other (living somewhere else) just exports the problem.
In the case of transportation, price is measured in time and convenience as well as dollars.
The idea of shrinking our roadways to discourage use of vehicles is challenging in a practical sense and it just cleaves off another aspect of life for business and the wealthy to enjoy without plebs interfering with the roadways they paid & still pay for.
If you widen streets and add more lanes, then more people drive, until they've filled up that street's capacity. But they don't really stop driving.