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?
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).
It's arleady $8 to cross the golden gate bridge. It's going to cost anohter how much exactly when I enter 'downtown'?