In the UK, it's very difficult now to drive your car and not be detected by an Automatic Number Plate Recognition (ANPR) camera. It is illegal to remove or deface your number plate so it can't be read by these cameras. This is an interesting parallel to the UK law requiring you to have your transponder on when flying. If you don't like having your car 'pinged' by cameras, ride a push bike. If you don't like your aircraft to show on radar or other sites, don't fly it!
TOO