One of best ways to increase parking revenue would be to set up a system to automate parking fees (similar to automated tolling).
I would gladly pay the $1 fee to park for 30 minutes in my downtown. However, I often skip paying because of the hassle of walking to the pay station, waiting several minutes to complete the transaction, and then putting the receipt back in my car.
If they just detected by license and sent me a bill, they could have my money!