Forth Road bridge is a suspension bridge with a main span of 1006 metres and side spans of some 408 metres. Approach viaducts to the north and south bring the total length of the structure to just under 2500 metres. The bridge was opened in 1964 and traffic has grown significantly from 4 million to 24 million vehicles using the bridge each year. All work carried out on the bridge has to be done under a regime of overnight or limited weekend of lane closures to minimise delays to users on this important stratergic and commuter route