Swing Bridge

A swing bridge is a movable bridge whose span rotates horizontally around a vertical pin and support ring, usually positioned near the span own center of gravity, to open a gap for boat traffic before closing again for road or rail traffic. Because the turning span is balanced on its own pivot, a swing bridge needs no counterweight, which makes it substantially lighter than a bascule or vertical-lift bridge of comparable size, though motors typically turn the span roughly ninety degrees, or as little as forty five degrees where it crosses a channel at an angle. Long-standing examples include the Carmelo Bridge in Uruguay, built in 1912 and considered the oldest swing bridge in Latin America, and Egypt's El Ferdan Railway Bridge, whose 340 meter swing span is the longest in the world.