But campaigners insist that the appearance of the devices is making dangerous driving more prevalent on the road.
Transport Scotland issued a statement saying that previous figures had shown that one in three drivers were exceeding the speed limit in the stretch between Perth and Pitlochry but this had now reduced to one in ten drivers following the installation of the average speed cameras in this area.
Measures to reduce driver frustration were also moving forward with the Scottish Parliament having now approved the legislation which will allow the HGV speed limit to be raised to 50 mph on single carriageway sections of the A9 when the cameras become operational in October.
Speaking ahead of a meeting with the Federation of Small Businesses in Inverness, Transport Minister Keith Brown said the multi-party A9 Safety Group was clear that average speed cameras were effective in saving lives and this was backed up by the facts. Before and after studies of other average speed camera sites in the UK showed a reduction in accidents. On average, they achieved a 61 per cent reduction in fatal and serious accidents.
"Average speed cameras encourage drivers to improve their behaviour and we are already seeing this on the A9. The Group is also taking forward measures to improve driver awareness of speed limits and to encourage safe overtaking on the route. Surveys have taken place in respect of driver's attitudes and experience of the route and further initiatives are being considered," Mr Brown said.
He continued: "When the camera system is switched on, the HGV 50 mph speed limit will also come into force with the backing of the Scottish Parliament. The pilot will introduce a level playing field for businesses which we expect will also benefit from less disruption caused by fatal and serious accidents.
He said an analysis of incidents on the A9 last year showed that the carriageway restrictions involved in dealing with these incidents totalled more than 540 hours.
He added: "That's the equivalent of over 22 days of restrictions on the A9 last year. The cameras will make connections safer and more reliable and will reduce the cost to the economy of serious accidents."
Superintendent Iain Murray of Police Scotland welcomed the reduction of speeding drivers on the A9. He said: "This is an early indication that drivers are already moderating their behaviour. This can only improve safety on the route and I would encourage all drivers to follow this example".
But Mike Burns of the 'Average Speed Cameras on the A9 Are Not The Answer' said "We have evidence that dangerous driving on that stretch has actually increased since the cameras went in. The fact is that journey times have increased by 40 minutes on that one section from Perth to Pitlochry with an average speed of 32 miles an hour because of the cameras. The drivers are telling us that as a result risky driving has increased in the last two weeks. Also it is a fact that support for our campaign has increased markedly, with more than 300 new supporters in the last few days."