If you're going to replace signs, how expensive would it be to just have one that changes from "Parking" to "No Parking" on a timer? My city already has similar signs for intersections that become no-left-turn when kids are around.
That doesn't tell you how long you can stay parked. How useful is it to know that you're currently allowed to park, without also telling you it's going to change to "No Parking" as soon as you've left your vehicle?
EDIT: If you could do a countdown timer to the next state, though, that'd be useful.
