Three Bridges, Three Centuries. Why Queensferry is special

The opening of the new Queensferry Crossing means the finest examples of civil engineering from the last three centuries now sit side by side by side across the Forth Estuary. Each bridge represented a leap in engineering at the time and broke new records.

All three bridges across the Firth of Forth
All three bridges across the Firth of Forth

The iconic Forth Bridge carrying the railway across the Forth is a Unesco world heritage site. Its solid 19th Century design was born in part out of the tragic collapse of the nearby Tay Bridge 11 years earlier. The structure was built out from the piers or supports - the longest single cantilever bridge in the world exceeded only by Québec Bridge some 40 years later after several failed attempts.

The 20th Century Forth Road Bridge was the longest suspension bridge in Europe when it opened in 1964. A much lighter and visibly more modern structure with the road suspended from steel cables - the first time this kind of bridge had been built in such a harsh climate. Suspension bridges are widely used around the world in preference to cantilever bridges for long spans but are vulnerable to the single point risk of weakening in the two critical cables.

The 21st Century Queensferry Crossing represents another stride in engineering innovation. The wonderful slender structure is again a record holder but the greatest step forward from the 20th Century Bridge is in resilience. The cable-stayed design with the road supported by many smaller cables brings resilience to the structure, with all the cables individually replaceable. The wind shielding along the roadway brings resilience for users, with the bridge capable of staying open in much higher winds.

ICE Scotland Chair Frances Ratcliffe said "What we have between Fife and the Lothians is a concentration of engineering excellence with three centuries of bridge design. These bridges not only provide the valuable transport infrastructure on which our economy depends, but they also enhance Scotland's skyline and contribute to a sense of place. The iconic bridges over the River Forth already attract tourists from around the world and the addition of such a beautiful and sympathetic structure only serves to enhance Scotland as a destination for many years to come."

Regional Director Sara Thiam added "Engineers are at the heart of ensuring our infrastructure remains resilient as climate change brings more frequent extreme 'weather events'. As with all best design, it is innovative, useful, aesthetically pleasing, and built to last. Engineering at its best."