Here's how. Your first thought may be to use a pet's name, a birth date, an address or parts of a phone number. These things are too easy for criminals to discover, so don't use them.
In a single week this month, the teacher has received three official warnings by text message to cover up, owing to traffic cameras that now flag license plate numbers with long-haired vehicle occupants.
As the cars come into the centre, video cameras record their registration numbers, and these are checked with a list of drivers who have paid the charge for that day.