So throw the baby out with the bath water? Great plan.

In cities? Yes. You start preferencing more space efficient modes of transport, and traffic jams go away, while transport time decreases. If you’re going to put a tunnel with fixed access points under a city, it makes a lot more sense to run trains than private cars.

If you’re going to have a 4 lane road reserve two of the lanes for super high capacity vehicles (busses).

Traffic jams are a byproduct of the limits of physics. Once you reach a certain density it is simply impossible to provide enough private car parking and lane capacity.