The rate of corrosion and weakening of the main cables would have required the bridge to close to HGV traffic some time around 2014 and then close to all traffic by 2019, so plans were drawn up to build a replacement crossing, to run parallel to the existing road bridge between Lothian and Fife. Dehumidification equipment was installed to remove moisture from the inside of the main suspension cables, in an attempt to slow or halt the corrosion, but with no guarantee of success, the Forth Estuary Transport Authority and Scottish Government were left with no option but to plan the construction of a new crossing.