This system goes live on 15th Feb and check the speed limits
Variable speeds are already used on the M25 west of London and the M42 on the edge of Birmingham. Cameras enforce the limits.
From February 15, all speed cameras will become digital in the variable speed limit section of the M25 from junctions 10 to 16 - the A3 junction to the M40 junction, the Daily Mail can reveal.
Until now, variable speed limit cameras on the M25 have used film, which limits the number of pictures that can be taken before the film has to be changed.
However, digital cameras can capture an almost indefinite number of images.
The "speed threshold" - the amount drivers can stray above the limit without getting a ticket - is also being lowered. Police sources say it will be set at 79mph.
Private company operated, so watch out for them making a killing.