The number fatal crashes on a stretch of the A9 has fallen by almost a third since the introduction of average speed cameras.

Cameras on the Dunblane to Inverness section of the road were switched on in October 2014 in an attempt to improve safety.

New figures published by Transport Scotland covering the 15-month period up to January 31, 2016, show the number of fatalities on the section was down 30%, while the number of fatal and serious collisions combined dropped by almost 44%.

The number of speeding vehicles between Dunblane and Inverness from October 2014 to April 24 this year is now one in ten compared to a historic benchmark of one in three.

Meanwhile, the average journey time between Perth and Inverness has risen by between one and nine minutes. Traffic on the route continues to grow at an average of 2.9% year-on-year.

A9 Safety Group chairman Stewart Leggett said: "The A9's improved road safety performance continues as the latest figures show the majority of drivers continue to respect the speed limits.

"The A9 is a safer place now than it was before the A9 Safety Group began its work.

"Fewer incidents are disrupting traffic and along this key route and these improvements have been delivered against a background of increasing traffic volumes and improved journey time reliability."

Average speed cameras now cover more than 250 miles of Britain's roads, according to a study published on Tuesday by the RAC Foundation.

Average speed cameras are now on 50 stretches of highway across the UK, with 12 new systems installed last year alone.

RAC Foundation director Steve Gooding said more research is needed to find out whether the overall frequency of crashes had been reduced since the average speed cameras were installed nationwide.

"Average speed cameras are becoming a more common fixture on Britain's roads," he added.

"Unsurprisingly, the indications are that compliance with the speed limit through stretches of road managed by average speed cameras is high, but the acid test is whether accident and casualty rates have also fallen. That is what the next part of this research project should tell us."