Most railway bridges over navigable water are high enough to allow ships to pass below.
The most common type of opening bridge on British railways is the swing bridge.
The new fixed span is carried on reinforced concrete piers with steel cross members, in place of the old timber ones.
A Railway Magazine article about this bridge, published in August 1955, can be found here.
The towers are each built off a 32 feet diameter concrete base, founded on clay at a depth of about 50 feet.This one is at Folkestone Harbour and is the third at this site.The first bridge was constructed in 1849, when the railway was extended across the harbour basin. The present bridge dates from 1930 and the deck is of steel plate construction.The Scherzer bridge survived long enough to carry electric trains, but for less than a year.Electric services to Sheerness started on 15 June 1959 and the new King's Ferry bridge was officially opened on 20 April 1960.There was a bridge which worked on similar principles at Newport, Isle of Wight.This carried the Ryde and Sandown lines over the River Medina.The Sittingbourne & Sheerness Railway provided a combined road and rail bridge at King's Ferry, with a lifting section to allow passage of shipping.Having taken responsibility for passage to the island, the railway company took the role of Wardens and Jury of the King's Ferry and were entitled to charge tolls to road users.Opening bridges are required where a railway crosses a navigable waterway without leaving sufficient headway for ships to pass underneath.There are relatively few of these in Britain, because inland navigation is mainly by small vessels, such as canal barges.