Speed cameras on the A17 in West Norfolk will be switched on next week, more than 10 months after they were first installed.
Road safety officials have also revealed that similar cameras are set to be installed on another of the borough’s busiest routes, the A149, later this year.
Seven average speed cameras were put in place on the section of the A17 between Lynn and Sutton Bridge in February last year.
But they will only start catching drivers who flout the rules when they become operational on Monday.
Anne Pointin, Norfolk Police road safety and safety camera manager, admitted the delay, which she said was caused by hold-ups in securing power supplies, had been “frustrating.”
But she said anecdotal evidence suggested the cameras were already having an effect on drivers’ behaviour.
She said: “The public perception is it is starting to slow people down.”
The A17 cameras were installed following a series of fatal collisions on the route in recent years.
The toll prompted calls for further safety measures, particularly around the Station Road turning at Terrington St Clement, which has been the scene of two of the fatal incidents.
Miss Pointin said: “This piece of road has double the national average for casualties on rural A class Roads, and the high accident severity is indicative of high traffic speeds.
“Thirty-five per cent of these casualties are motorcyclists and the new cameras are designed to capture both motor vehicles and motor cyclists.”
She also confirmed officials are looking to install similar cameras on the A149, between the Knights Hill and Dersingham roundabouts, in response to a similarly high record of fatalities and serious injuries there in the last few years.
She said: “At the moment, we’re working with the county council on where exactly they would go.
“If all goes according to plan, we would be looking to install them in the latter part of this year.”
The installation of cameras on the A17 has prompted calls for similar measures on other routes including the A47 around Middleton, East Winch and West Bilney, and the B1145 between Lynn and Gayton.
Lorne Green, Norfolk’s police and crime commissioner, said: “Road safety is a big concern for many of Norfolk’s residents, with excessive speed being one of the Fatal 4 factors which put road users at risk.
“Enforcement of the law, alongside sustained education and awareness, will help keep our county’s roads safer for all who use them, and speed cameras have an important role to play in that.”