The three bridges are: nearest, the Queensferry Crossing, a cable-stayed road bridge, opened in 2017; the Forth Road Bridge, a suspension road bridge, opened in 1964 (at which time it was the longest suspension bridge in the world); and, furthest from us, the Forth Bridge, a cantilever rail bridge, opened in 1890.
The Forth Road Bridge had a design capacity of 11 million vehicles per annum. By 2006 it was carrying 23 million vehicles p.a., and this huge load was causing significant wear on the structure, significantly reducing its lifespan from the originally planned 120 years.
The decision to build the replacement bridge was taken in 2007, following the discovery of corrosion on the main cables. The Forth Road Bridge has now reopened as a dedicated public transport corridor. In May 2023 trials began of a driverless bus service connecting Inverkeithing on the north side with Edinburgh on the south side.
Meanwhile, the Forth Bridge continues to carry rail services between Edinburgh and the north. The maintenance of the bridge, mostly involving painting the iron structure repeatedly to prevent corrosion, became a famous metaphor for a never-ending task, but beginning in 2002 the bridge was completely repainted with with a new paint specifically formulated for the bridge. As a result it is expected the bridge will now only need to be repainted every twenty years.