A higher speed limit for HGVs on the main route into the Highlands will come into force when new speed cameras are switched on next week.

Legislation to allow HGVs to travel at up to 50mph on the busy A9 between Perth and Inverness has just been signed.

It will come into effect from Tuesday October 28, the same day that average speed cameras on the road become operational.

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.

HGVs are currently allowed to drive at up to 40mph on the A9, which can lead to queues of traffic building up behind them on single carriageway stretches.

Transport Minister Keith Brown said the pilot project to up the speed limit is "part of a package of measures that is being taken forward to improve the operational performance of the A9 and to enhance safety".

He said: "We want to see reliable and competitive journey times for all road users, including the freight haulage industry. Simply raising the speed limits for HGVs could have a detrimental effect, but the use of average speed cameras as part of the pilot helps support the wider changes we are making to promote an overall improvement in driving conditions.

"The 50mph HGV pilot will bring operational benefits and help reduce frustration on Scotland's longest road."

Richard Burnett, chief executive of the Road Haulage Association, said: "The key issue here is one of improving journey time reliability for hauliers and other road users alike.

"Many A9 incidents, together with the resultant delays, are caused by no more than sheer motorist frustration when getting stuck behind a slow moving heavy goods vehicle. It makes sense that a 10mph reduction in the speed differential between cars and HGVs will mean a corresponding reduction in frustration and accidents.

"In addition to improved efficiency, as most modern trucks do not get into top gear at 40mph, there are potential safety benefits. This really is a win-win situation for all users of one Scotland's major arterial routes."

Malcolm Bingham, the Freight Transport Association's head of road network management policy, backed the pilot and added: "We welcome the opportunity for such a trial as we believe the current differential in speed limits between HGVs and other vehicles increases the road safety risk."

There are no plans to change the speed limit for HGVs on any other roads in Scotland.