Data capture involves mechanisms to gain and read an image of a vehicle number plate (aka registration plate). Most jurisdictions require that motor vehicles be identified through an alphanumeric sign at the front and rear of that vehicle, with the sign generally being of a standard size and a common font. The identification 'numbers' on that plate are drawn from a register maintained by the particular jurisdiction. That database typically features information about ownership of the vehicle and may be tied to a discrete database of registered drivers, ie those people with a drivers' licence.

Applications
In principle, ANPR provides a basis for any scheme that is restricted to or that leverages vehicle registration information.
Applications in Europe and Australia have thus included -

• traffic congestion management (differential pricing for use of roads in a precinct)
• traffic speed restrictions
• offender identification (unregistered, uninsured, stolen vehicles, fake number plates)
• criminal intelligence (location of terrorism suspects and 'persons of interest to the police')
• generation of blacklists of vehicles seeking fuel or other products from petrol stations

Speed Restrictions
ANPR can also be used for automated enforcement of speed restrictions and associated traffic codes, such as prohibitions on particular classes of vehicles (such as those carrying explosives or chemicals) using specific routes. Speed restriction is mechanistic, with the ANPR system 'logging' the vehicle at two or more locations and determining whether transit between those points and times breached speed limits. A billing database can then automatically issue a fine and/or alert traffic police that a breach is underway.

Offender Identification
Law enforcement officials appear to have been more enthusiastic about the scope for using ANPR in 'offender identification'.
That encompasses such things as identification of -

• unregistered vehicles, ie vehicles with an expired number plate (significant because most regimes prohibit driving of an unregistered vehicle but do not require that 'unused' vehicles have a current plate)
• uninsured vehicles (primarily in regimes where it is mandatory to insure a vehicle through a government-controlled insurer)
• stolen vehicles (ie where the thief takes the vehicle but does not change the number plates)
• vehicles with cloned plates (eg the same plates are identified on separate vehicles in different locations at much the same time) or with bogus numbers (eg there is no match with the vehicle register)
• vehicles engaged in activity such as unauthorised use of bus-only lanes.

Such identification can be tied to automated issue of a fine or summons to appear before a magistrate. It can also be used in real time to alert law enforcement personnel to intercept the suspect vehicle, for example to find and pull over a car that has been reported as stolen.

Criminal Intelligence
Police, customs and other law enforcement officials are reluctant to tightly circumscribe use of ANPR. As the following pages note there appears to be considerable sharing of information by agencies and real time checking of plates against multiple hotlists.

Such lists include vehicles -

• reported to have been involved in hit and run incidents, petrol thefts, drive by shootings, burglaries and abductions
• reported as having been at the scene of a crime
• registered to suspected terrorists, family and associates
• rented using 'flagged' credit cards
• registered to suspected drug traffickers or child sex offenders
• registered to suspected stalkers

In practice a wide range of people may be 'of interest to the police' (and their peers); the major limit on realtime large scale ad hoc sorting based on ANPR is the difficulty of linking different databases.