Picture of a ANPR Automatic Number Plate Recognition van watching the A1 in North Yorkshire.

The cameras scan and record the vehicle registration marks of every passing car.

The numbers are then cross-checked against the Police National Computer, the DVLA databases and police intelligence records, both locally and regionally, to identify vehicles of interest to the Police.

The cameras can check up to 3,600 number plates an hour on cars travelling in excess of 100mph.

ANPR is estimated to be around ten times more effective than normal traffic policing because its spots suspect vehicles that may not normally attract police attention.