While the code barcode breakdown in this article is cool, I doubt you could actually use it to get free parking (which is not ethical anyway). My guess is that

While the code barcode breakdown in this article is cool, I doubt you could actually use it to get free parking (which is not ethical anyway). My guess is that the system records the barcode it printed when you enter. So, when you exit and scan your forged ticket, it will probably say that it doesn't recognize the ticket because the barcode was never recorded in the system on entry.