One in 10 parking fines issued as a result of scans made by cars using automatic number plate recognition systems is unjustified, privacy watchdog Autoriteit Persoonsgegevens (AP) has calculated.

The cars are equipped with special cameras which can check parked cars more efficiently than inspectors on foot, making them an attractive alternative for local councils.

The cars tot up between 250 million and 375 million scans a year, resulting in three to five million fines. In 500,000, or 10%, of the cases, the technology gets it wrong, the AP found, following a study of local council data.

For example, the scanners are unable to judge why a car has been parked.  If people are loading or unloading the car, for instance, they may not be breaking the rules. The camera also fails to register disabled parking permits placed at the front of the car. These are not automatically linked to the number plate, resulting in a fine.

Contesting a fine is laborious, time-consuming and not transparent, the AP said. Just 40% to 62% of motorists stay the course and get the fine annulled.

The AP said the shortcomings in the system hit vulnerable people like the disabled and those who have trouble coping with the digitalisation of the parking process.

The AP wants local councils to improve the system by strengthening physical controls and ascertaining how many wrongful fines were issued in order to evaluate the process.

Not all local councils comply with the requirement to investigate and limit the risk to privacy before using a scan car or properly check that commercial companies carrying out the policing process are operating within the law. That too needs to change, the AP said.