Vertical-Lift Bridge

A vertical-lift bridge is a movable bridge whose entire span rises straight up while staying level and parallel to its own deck, rather than tilting like a bascule bridge or turning like a swing bridge, so a train or heavy load can cross without the deck ever leaving the horizontal. Because a lift bridge's counterweights only need to match the weight of the deck itself, rather than several times that weight as a bascule bridge counterweights must, engineers could build heavier, longer decks suited to rail traffic, and the type became especially common around the Great Lakes as steam vessels needing tall clearance met increasingly heavy rail lines. An early railway example was built in 1834 to a design by Robert Stephenson on the Leicester and Swannington Railway, and the oldest such bridge still operating is the Hawthorne Bridge in Portland, Oregon, completed in 1910; the design chief drawback is that raised or not, the deck resting height still limits the size of vessel that can pass beneath it.