The system only works if people are honest with it. If they run out and change the time on the disk every 90 minutes then it doesn't work well.

On St Barth, they use uniformed municipal employees to write the tickets. I managed to get a ticket when I forgot to set the disk.

The blue disks areas in Gustavia are 90 minutes, and I think the ones at the airport are 20 or 30 minutes, with a pay lot across the street. The main parking lot in Gustavia is now a pay lot with a central pay station. I'll figure out how that works the next time that I'm over there.