Hundreds of motorists are being caught speeding daily by a series of linked cameras on the M1 near Leicester.
Cameras work out drivers' average speed through the works
They measure drivers' average speed through the stretch being resurfaced from junction 21 at Leicester towards junction 20 at Lutterworth.
Speed cameras normally check speed at a specific site, but motorists are being clocked by a series of cameras which work out speed over a longer stretch.
Some 2,000 fines have been handed out in the last fortnight.
Roadworks will be in place until November, affecting several miles south of the main junction into Leicester and the start of the M69.
Richard Lea reminds drivers they pass within feet of men at work
The first major set of work in 20 years on this stretch should reduce the amount of traffic noise in the area, with a 40mph limit operating 24 hours throughout the five months of work.
Stretches of the southbound carriageway have already been resurfaced. It is currently divided into five narrow lanes of contra flow traffic while work continues on the northbound carriageway.
The stretch of motorway carries about 100,000 vehicles a day - with 300 being caught daily by the cameras.
Richard Lea, a safety officer for Optima, carrying out the work, said: "We need to make the travelling public aware of safety. They are passing within feet of people working."
He said they need to keep in the correct lane and take note of the lower speed limits.