Clyde Tunnel (Glasgow)

 tunnel, invisible, draw only border

The Clyde Tunnel is 762 metres long - approximately 7 football pitches. It is 21 feet (6.4m) below the river surface, depending on the tide. Approximatly 9000 vehicles use the tunnel each day. In 1964 it was the steepest tunnel ever built. (1 in 16 ratio or 6%). If you imagine a piece of string looped between your hands, (your hands represent the tunnel ends) the deeper the loop, the closer your hands are. Engineers calculated the depth so that the tunnel would connect to existing roads. It replaced the Govan and Renfrew ferry services. Work on the tunnel stated in July 1957 and the first tunnel opened on July 1963 with the second tunnel opening a year later. it cost £10.5million (in todays money, £200million)