Bridges: Built on a Firm Foundation
Gwendolyn Robinson
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Drawbridges have a roadway that is moved entirely or partially to provide enough clearance for large ships to pass. There are three types of drawbridges, bascule bridges, lift bridges, and swing bridges. A bascule bridge tilts upward to open. Some bascule bridges open at one end, and others open in the middle. A lift bridge has a roadway that extends between two towers. The roadway rises between the towers, and ships pass underneath. A swing bridge is mounted on a central pier. The bridge swings sideways to enable ships to pass.
An example of the lift type of bridge is the Tomlinson Bridge