Transport chiefs have removed signs placed on the controversial average speed cameras along the A9 to avoid confusing drivers.
When the gantries were installed in Perthshire earlier this year they were accompanied by placards stating “cameras under test”.
However, the signs disappeared this week and Transport Scotland has denied this has anything to do with motorists thinking their movements were being recorded.
A spokeswoman for the Scottish Government agency said: “The installation of the average speed cameras is subject to a rigorous testing programme required to meet Home Office approvals.
“During this process the cameras are not used for enforcement purposes and no data is retained by the system.
“The ‘cameras under test’ signs have been removed as a more appropriate messaging is being introduced to advise drivers on the route of the status of the cameras.
“The temporary signs are being replaced with variable messaging signs which will allow us to promote wider messages as required.”
According to Transport Scotland data, driver behaviour is already improving, with the number of speeding motorists dropping from one in three to one in 10. It also claims that journey times have increased by only three minutes over 24 miles.
But regular road users have hit out at the £2.5 million system, reporting a significant change in driver behaviour.
One campaigner claimed he recorded average speeds as low as 32mph in camera zones, describing it as a “complete farce”.
Meanwhile, other drivers have reported queues of between 40 and 50 vehicles, as well as an increase in dangerous overtaking.
The plans cover the entire 136-mile route between Dunblane and Inverness as part of efforts to cut the number of crashes before the road is upgraded to dual carriageway by 2025.
Cameras will be installed every three to four miles along single carriageway parts of the A9 between Perth and Inverness and along the dual carriageway between Perth and Dunblane.
Earlier this month Transport Scotland said drivers would be fined £100 and given three penalty points each time they were caught by an average-speed camera on the A9 between Inverness and Perth.