Transport Scotland insists the presence of average speed cameras on the A9 will slow down traffic.
The Scottish Government agency spoke out after viewing a video of a dangerous overtaking manoeuvre on the road highlighted by campaigners.
A TS spokeswoman said: “Inappropriate and unsafe overtaking is one a range of behaviours that is unacceptable on the A9.
“The presence of average speed cameras will allow Police Scotland to target these instances more effectively using their dedicated trunk road policing resources.
“It is incumbent on all A9 users to drive to the conditions, local circumstances and relevant speed limits during the course of their journeys.”
The spokeswoman said the camera scheme was part of a package of measures being introduced which included engineering improvements and education measures.
Scottish Government claims cameras will discourage speeding