New figures show there were six people killed on the road in the first year of the cameras, compared to an annual average of eight deaths in the three years before they were installed.
The number of people seriously injured fell from 20 to four, while fatal and serious collisions dropped from 17 to seven, a 59% fall.
There were no fatal collisions anywhere on the A9 in the last six months of 2015, the longest period in Transport Scotland’s accident database which reports back to 1978.
Transport Minister Derek Mackay said: “We are monitoring the performance of the A9 and welcome the figures which indicate that the route continues to perform far more safely than before.
“Fatal and serious casualties have more than halved and there are clear and substantial reductions in fatal casualties both between Perth and Inverness and between Perth and Dunblane.
“Every road death is one too many and that is why we remain steadfastly committed to reducing casualty numbers even further as we continue to work with all our partners to reach our ambitious targets for 2020.”
Police Scotland said the latest quarterly data from the speed cameras showed low levels of drivers being reported, with figures indicating an average of five drivers a day exceeding the limit.
Since the cameras were introduced, just over 6,000 vehicles have been caught speeding, out of more than 18 million journeys along the route.
Chief Superintendent Andy Edmonston said: “The reduction in serious and fatal injury collisions on the A9 in the first year following installation of the safety cameras is welcome.
“However, while the number of fatalities decreased by a quarter, the case remains that six people sadly lost their lives on the road.
“We can never be complacent and Police Scotland will continue to maintain a visible presence on the A9 to promote safety and positively influence driver behaviour.”
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