Scotland’s first ‘intelligent transport system’ (ITS) has gone live in Fife as part of the project to build a new Forth crossing.
Vehicles on the M90 are now monitored by sensors to detect when there is traffic congestion.
During heavy traffic the speed limit is lowered with the aim of preventing jams, reducing journey times and cutting carbon emissions.
Sensors in the carriageway were switched on as commuters made their way across the Forth Road Bridge on Tuesday.
The M9 and M9 spur near Kirkliston are set to be fitted with ITS early next year and by the time the new bridge is ready in 2016 the system will extend for more than 13 miles, from the Halbeath junction to West Lothian and the M9 Newbridge junction.
Transport Minister Keith Brown said: ”The Forth Replacement Crossing is a flagship project for the Scottish Government’s determination to invest in our national infrastructure and, in turn, protect and grow our economy. And it is already delivering.
”The project, which is on time and on budget, was always about more than just the building of a new bridge, as impressive a feat of civil engineering as that stunning structure will ultimately prove to be.
”It was about improving that vital cross-Forth link and using existing infrastructure more efficiently to ensure better traffic flow and more reliable journey times, prioritised public transport, improved safety and lower emissions.”
Mr Brown said officials in Transport Scotland have undertaken an extensive information campaign including radio adverts and online content.
Seventeen overhead gantries have been installed on the M90 to inform drivers of variable speed limits.