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.
Anyone caught breaking the limit - 60mph for cars and 50mph for lorries - in just four of the eight zones would clock up 12 penalty points, enough for a ban.
Campaigners yesterday claimed the measures could actually cause accidents, by focusing drivers' attention on the cameras rather than other hazards.
The Scottish Government says the £2.5 million scheme will cut speeding and improve safety until the road is upgraded to dual carriageway by 2025. The cameras are to be switched on in October.
However, Highland Liberal Democrat MP Danny Alexander has vowed to keep up his efforts to get SNP ministers to scrap the scheme.
Mr Alexander and the leader of a campaign against the devices, Mike Burns, claim they will increase frustration and accidents.