The work, which will take six months, will involve lane closures and temporary traffic lights, but officials said “no significant delays are expected for motorists”.
Cameras which measure vehicle speeds over set distances will be erected at 27 sites within seven stretches of single carriageway on the main route between the Highlands and the Central Belt.
However, completion of the £2.5 million scheme has been delayed from this summer until October and will not now cover dual carriageway sections north of Perth, as The Scotsman revealed last month.
Details of camera installation on the A9 between Perth and Dunblane have still to be announced.
The system is designed to reduce crashes and casualties, but opponents argue it will not cut driver frustration in slow-moving traffic that can trigger dangerous overtaking manoeuvres.
Stewart Leggett, chairman of the A9 Safety Group, which includes Transport Scotland and police, said: “This work is the first stage of the installation of the cameras and we have worked hard to make sure that this is done with the minimum disruption for road users.
Eddie Ross, of BEAR Scotland, said: “Works have been carefully planned and we will endeavour to undertake them with as little disruption to road users as possible.
“We would ask for motorists to be patient during this time and their support whilst we undertake these important safety works is appreciated.