The M1 through Nottinghamshire and Derbyshire is to get permanent speed cameras to enforce variable limits.
Temporary cameras installed for widening road works between junctions 25 and 28 have proved so effective they will stay, it has been confirmed.
Once the work finishes the stretch will become a "managed motorway" with speed limits changing to suit conditions.
Police said matrix boards would display the chosen limit and these would be enforced by the cameras.
Ch Insp Andy Charlton, of Nottinghamshire police, said: "When the project finishes, that stretch of motorway will become a managed stretch of motorway where the cameras will be used to enforce variable speed limits.
"While they are there temporarily at the moment as a time distance section, in the future when the M1 [widening] is finished there will be variable speed limits, up on the matrix boards, and they will have camera support".
Between May 2008 to October 2009, 5,084 vehicles were recorded as breaking the 50 mph limit, on a stretch used by about 131,000 vehicles daily.
Work began to widen the 14-mile stretch of the motorway in November 2008 and the project is due to finish this autumn - but the highways agency has said it could now be earlier.