The latest in a series of average speed cameras is being installed on the outskirts of Perth.
The new unit is to be put in place on the A9 near Windyedge Farm, about two-and-a-half miles south of the city.
Transport Scotland said the work is due to continue until Wednesday October 15. A stretch of the nearside carriageway will be shut while installation is being carried out.
The equipment is one of 27 camera columns being constructed to monitor traffic speeds between Dunblane and Inverness.
They are due to go live later this month. Work on the A9 is believed to have contributed to major tailbacks on surrounding roads during the morning rush hour opn Monday.
A two-mile traffic jam was reported along the nearby M90 between the Broxden roundabout and Craigend.
Police said there were no major incidents on the roads and believed roadworks and torrential downpours could have caused delays.
The speed camera plan was announced by transport minister Keith Brown at Blackford last year.
