Average speed camera enforcement on single-carriageway sections of the A9 has delivered up to 50% reductions in incidents of killed or seriously injured (KSI) road users since its installation in October 2014, Transport Scotland has claimed.
Transport Scotland's head of the Scottish Safety Camera Programme, Luke Macauley, made the claim for the system, which was introduced to cut dangerous levels of overtaking, at ITS (UK)'s 2015 Enforcement Conference on Wednesday.
He also said that journey times have stabilised to meet pre-set baselines, while traffic volumes continue to grow.
Compliance levels of 99.96% have been achieved on the central stretch of the 439km-long 'spine of Scotland' which crosses the Grampian Mountains.
It had experienced over 100 road deaths during the previous eight years, when it was covered by police cars and mobile speed camera vans.
Social media, Mr Macauley said, had played a major role in winning over public opinion, which was initially hostile, and there was now widespread acceptance.
The cameras have been installed at 27 regularly-spaced sites at a cost of £2.5m. A long-term. £3bn programme to dual 128km of the route between Perth and Inverness by 2025 got under way in September 2015.
The cameras will be dismantled once this is completed as a permanent solution to the overtaking problem.