Well then the obvious solution is to make downtown driving expensive. Charge money to enter downtown
Then they have even more incentive to remain downtown circling around.
Until they run out of fuel. Then you have them pay more for that as well.
Charge $2 / 15mins for a SDC to be present downtown?
It's arleady $8 to cross the golden gate bridge. It's going to cost anohter how much exactly when I enter 'downtown'?
Bill vehicles according to the length of time spent in the area, minus any period spent off-road in a parking facility or similar (which will presumably be charged separately by the operator of the parking facility).