The Auchenkilns interchange on the eastern fringe of Glasgow is open after almost two years' work. A roundabout at the junction has been replaced by a flyover with four slip roads connecting with a bridge over the A80.
Other roads leading to the junction are being realigned to ease traffic flows.
The interchange is one of the busiest intersections in the area and carries around 70,000 vehicles every day. The A80 is the main trunk route into Glasgow from Falkirk and Stirling.
Scottish transport minister Tavish Scott commented: "These improvements will bring real benefits to road users by improving safety, tackling congestion and shortening journey times."