[wbsgrepit]

I think he is forgetting that the barcode is generated and exits not in a silo but with knowledge of a controller. I would be amazed if the system did not both track the barcode creation and exit events and trigger protocols on any outside system event.

Print out your card at home, park at lot, scan to checkout, your barcode is in one of three states: 1: Not valid because it has not been issued by the controller, 2: Valid and first use (you left before the other car on the lot with the duplicated barcode has exited), 3: Invalid because it has already been used on exit (the duplicate barcode has already left the lot).

In what scenario given an active controller that is not braindead would this give you any kind of advantage? You are more likely than not going to be in a situation where you trigger an alarm on exit.