In the early 1990s, the Marsh Mills junction was significantly remodelled, reducing the size of the roundabout and building a flyover over the top of it, allowing free flowing access from the Plympton bypass onto the Parkway. The viaducts carrying the A38 over the River Plym, which after the construction of the Marsh Mills flyover became the Exeter bound sliproads, were built in 1969–70 as part of the Plympton bypass. They were replaced in the 1990s due to suffering from Alkali Silica Reaction, and the project, completed in February 1996 at a cost of £12.25million, involved the world's largest sideways bridge slide at the time for the , 5,500 tonne bridge. This required the road to be closed for only 48 hours, which won it an AA National Motoring Award in 1996 for innovation and minimisation of traffic congestion.