Operation Agra involving Cambridgeshire and Essex police forces uses Automatic Number Plate Recognition (ANPR) to monitor traffic across county borders.

The technology instantly traces number plates on cars to see if the vehicles have been stolen or used in crime.

If the vehicles are on a blacklist, the drivers can be pulled over and questioned within seconds.

The aim is to catch offenders, such as drug dealers or car criminals, who use the M11 as a main route.

The crackdown follows a similar joint operation between the forces in July last year which led to several arrests.

The Cambridgeshire ANPR unit situated at the junction with the A505 at Duxford surveys traffic travelling in both directions.

Stolen vehicles

Vehicles heading south are monitored by Essex officers on a bridge further along the motorway.

ANPR identifies stolen vehicles or those which have been involved in crime.

These vehicles can then be pulled over by traffic officers further along the motorway.

Sgt Tim Elliott, who is running the operation, said: "We will not be stopping people randomly.

"This is intelligence-led policing, in partnership with a neighbouring force, aimed at combating crime in the region."