AVERAGE speed cameras on one of Scotland's most notorious roads have been switched on as part of a plan to improve safety and save lives.

Construction work on the new system for the A9 between Perth and Inverness began in May.

In addition, a higher speed limit for HGVs on the route came into force yesterday, with a view to reducing driver frustration caused by slow vehicles on the busy road. The increase from 40mph to 50mph on single-track roads is being trialled under a pilot project.

It is hoped both measures will help reduce the accident rate on the A9, which is the main road between central Scotland and the Highlands.

It is commonly regarded as one of the country's most dangerous roads, with fatal and serious road accidents on the single carriageway between Perth and Inverness significantly higher than the national average.

Transport Minister Keith Brown said: "The facts are clear that average speed cameras are effective in saving lives."

Work on the new camera system saw columns, cameras and infra-red lighting masts erected on the single carriageway sections.

Earlier this year, figures suggested the presence of the newly installed cameras was already cutting drivers' speed - even though they had not been switched on.

Environmental group WWF Scotland has called for average speed camera schemes to be introduced on more of the country's roads.

Climate and energy policy officer Gina Hanrahan said: "Alongside the clear safety benefits, enforcing speed limits using average speed cameras and other tools is an effective way to reduce climate emissions as well as fuel costs for motorists."