The Firth of Forth is an estuary on the east coast of Scotland, and also the mouth of the River Forth to the North Sea. The new bridge, which will be called the Queensferry Crossing and which sits alongside the existing Forth Road Bridge (FRB) built in 1964, is under construction to safeguard the cross-Forth M90 motorway corridor following concerns about the long term viability of the FRB.