The introduction of average speed cameras on the A9 has cut the number of deaths on the road by a third, new figures reveal.

Since the cameras were switched on in October 2014, there have been eight deaths compared to the previous 18-month average of 12.

The number of serious injuries between Dunblane and Inverness was down by almost three-quarters from 30 to eight.

The A9 Safety Group said there had been a "sustained improvement" in the behaviour of drivers on the road, with the number of speeders falling from about one in three to one in ten.

Chairman Stewart Leggett said: "Since the cameras were introduced there has been a sustained improvement in driver behaviour and we are now seeing a corresponding fall in casualties.

"The A9 Safety Group is heartened by the early outcomes and as the dualling progresses we will build upon the early work of the Group to maintain the improved driver behaviour and support further casualty savings."

The most recent figures, published on Tuesday, include data from when the cameras were switched on in October 2014 to April this year.

Transport minister Humza Yousaf welcomed the figures, saying: "Safety is an absolute priority and every road death is one too many.

"The latest A9 Safety Group figures indicate the route is much safer since the average speed cameras were introduced.

"The data marks the mid-point in the three year evaluation period and, shows that four fewer people have been killed, 22 fewer seriously injured and 62 fewer people slightly injured.

"This extremely encouraging picture is to be welcomed and I would urge all A9 users, particularly the small minority who continue to take risks, to play their part in reducing accidents as we progress our £3bn A9 dualling programme."