Average-speed cameras will cover the seven single carriageway 60mph sections between Perth and Inverness, but also the continuous 70mph dual carriageway section between Perth and the Keir Roundabout, south of Dunblane.
Since 2008, 74 people have been killed on the A9 between Dunblane and Thurso, including nine last year and seven this year.
The launch of the cameras will coincide with the lorry speed limit on the single carriageway sections being raised from 40mph to 50mph for a three-year trial period.
The cameras measure vehicle speeds over set distances, but as they are positioned every few miles, motorists will not know over which stretch they are being monitored.
Ministers believe the cameras will reduce the number of crashes and casualties, but critics say the scheme will not address the problem of dangerous overtaking.
They are seen as an interim before Perth-Inverness section of the road is fully dualled by 2025.
Highland Liberal Democrat MP Danny Alexander, who has led a campaign against the cameras, claimed most people in the region opposed them.
He said thousands had signed petitions.
Mr Alexander, who is the UK Government’s chief secretary to the Treasury, said: “We all want the road to be safer, but most Highlanders believe the SNP is making a grave mistake by ploughing on with this scheme, because it will increase driver frustration and risk on the road.”