A £250,000 camera system has gone live along a popular tourist route and accident blackspot.
Average speed cameras have been installed on a 16-mile stretch of the A82/A85 between Tyndrum and Lix Toll.
One in three motorists were previously recorded speeding when fixed mobile cameras were in place.
Over a three-year period, there were 21 accidents resulting in injury – including one fatality and 11 collisions with serious casualties.
The hope is the new system will change the way motorists behave.
Transport secretary Michael Matheson said: “The positive impact average speed camera systems have in improving road safety has been evidenced from other areas in Scotland.
“We remain committed through Scotland’s Road Safety Framework to 2020 to making our roads safer, and we are working towards an ultimate vision of zero fatalities and reduced number of serious injuries on our roads.”
The road carries a high volume of commercial, local and tourist traffic heading through Loch Lomond and The Trossachs National Park.
The new cameras are located 3 to 4.5 miles apart at six sites, with cameras operating in each direction.
Gordon Watson, chief executive of Loch Lomond & The Trossachs National Park, said: “This is a key route through the north of the National Park but has unfortunately experienced a high number of collisions and speeding incidents in the last few years.
“We want everyone visiting and living here to be able to enjoy the area safely so we welcome the introduction of these average speed cameras that have been designed to help maintain the look and feel of the road network in the National Park.”