Automatic number plate recognition[ANPR] is a mass surveillance method that uses optical character recognition on images to read the licence plates on vehicles. As of 2006, systems can scan number plates at around one per second on cars travelling up to 100 mph (160 km/h). They can use existing closed-circuit television or road-rule enforcement cameras, or ones specifically designed for the task. They are used by various police forces and as a method of electronic toll collection onpay-per-use roads and monitoring traffic activity, such as red light adherence in an intersection.
ANPR can be used to store the images captured by the cameras as well as the text from the licence plate, with some configurable to store a photograph of the driver. Systems commonly use infrared lighting to allow the camera to take the picture at any time of the day. A powerful flash is included in at least one version of the intersection-monitoring cameras, serving both to illuminate the picture and to make the offender aware of his or her mistake. ANPR technology tends to be region-specific, owing to plate variation from place to place.
Concerns about these systems have centered on privacy fears of government tracking citizens’ movements and media reports of misidentification and high error rates. However, as they have developed, the systems have become much more accurate and reliable.
ANPR is sometimes known by various other terms:
- Automatic licence plate recognition (ALPR)
- Automatic vehicle identification (AVI)
- Car plate recognition (CPR)
- Licence plate recognition (LPR)