Automatic license plate recognition
Automactic license plate recognition (also called automatic number plate recognition in Europe)(ALPR) is a mass surveillance method that uses computerized optical character recognition on images to read vehicle license plates. The images to be analyzed can come from red light cameras, speed cameras, closed circuit television security camera or portable cameras mounted on police cars.
Some systems use infrared light cameras instead of visible light to get a higher contrast image.
ALPR can be used in conjunction with radio frequency identification (RFID) to collect tolls or enforce HOT lanes. ALPR can also be used to enforce traffic laws if cameras are programmed to capture vehicles that run a red light or that exceed the posted speed limit.
Although police may initially capture license plate data for parking enforcement or toll collection, if the data is retained and placed in a data base, it can be used to track the location and movement of citizens over a period of time. Essentially, it is monitoring and recording the movement of citizens without probably cause or a warrant. Some states are now adopting statutes to limit the amount of time that such license plate data can be retained by police.