ALPR 'reads' Vehicle Lisence Plates from digital images, captured through cameras located either in a mobile unit, in-built into patrol vehicles or static Closed Circuit Television.

The digital image is converted into data, which is processed through the ALPR system. This system is able to cross reference the data against a variety of databases.

Once the data has been cross checked against these databases - a process that takes around 1.5 seconds to complete - the information supplied via the ALPR system alerts officers to an offence or relevant intelligence on a vehicle, the vehicle will be stopped to allow officers to investigate further. ALPR officers acting as 'interceptors' also use their observation to stop other offenders not highlighted by the system. ALPR systems are able to check up to 3,000 number plates per hour, per lane, even at speeds of up to 100mph.