National Highways apologised for the error.
“Safety is our number one priority,” said chief executive Nick Harris.
“All drivers should continue observing the posted speed limits as normal. Anyone who has been impacted will be contacted by the relevant police force.”
The agency said a temporary fix had been rolled out, providing an extra layer of data from the cameras to police forces so they can filter out any faulty captures.
But the agency gave no clear timeline as to when a permanent fix would be in place.
National Highways, which runs England’s motorways, blamed an “anomaly” in how variable speed cameras were interacting with signs on some A roads and motorways.
It meant a delay of around 10 seconds between cameras and relevant variable speed signs, meaning some drivers were incorrectly identified as speeding after the limit had changed.
So on a road where the speed limit increases, a driver may see a sign saying 60mph, but the camera recording it may still be working on the basis of a previous 40mph speed limit.
National Highways said the 2,650 incidents since 2021 represent fewer than two each day, compared with more than six million activations of speed cameras on the affected roads over the same period.
It said the anomaly has impacted 10% of England’s motorways and major A roads.
The fault affects 154 cameras out of a total of 400 across the entire motorway network – all of the variable speed cameras on smart motorways, and a section of the A14 between Huntingdon and Cambridge plus the A1 approach junction to the A14.
