NYCDOT - About Movable Bridges

New York City Department of Transportation

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	Bridges About Movable Bridges

	Basically, movable bridges come in four 'flavors,' and New York City is fortunate enough to have examples of all of these. On this page, we'll give brief descriptions of each of the four types of movable bridges - supported with photographs or sketches. In addition, we'll offer a lay person's perspective on how each type of bridge works. The four types of movable bridge are: Bascule Retractile Swing Span Vertical Lift Bascule Easily the most popular type of movable bridge in existence today, bascule bridges are designed to pivot on a fixed axis. Usually this type of bridge consists of movable 'leaves' fixed to each end of the channel. The leaves are precisely counterbalanced by weights of sufficient size that relatively little motor power is required for their operation - usually just enough to overcome inertia, frictional resistance, wind and snow loads. Bascule bridges are simple and speedy to operate, and because of the relatively small amount of electricity needed for movement, cost efficient. There are 12 Bascule bridges under the control of the NYCDOT. 1. Eastern Blvd., a highway bridge over the Bronx River 2. Hunters Point Ave., a highway bridge over the Dutch Kill 3. Metropolitan Ave., a highway bridge over the English Kill 4. Hamilton Ave., a highway bridge over the Gowanus Canal 5. Third St., a highway bridge over the Gowanus Canal 6. Union St., a highway bridge over the Gowanus Canal 7. Hutchinson River Pkwy., a highway bridge over the Hutchinson River 8. Pelham, a highway bridge over the Hutchinson River 9. Mill Basin, a highway bridge over the Mill Basin 10. Greenpoint Ave., a highway bridge over the Newtown Creek 11. Pulaski Ave., a highway bridge over the Newtown Creek 12. Unionport, a highway bridge over the Westchester Creek Retractile This type of bridge is mounted in a skewed position on trucks or carriages on one side of a body of water. To open the channel to waterway traffic, the bridge is "retracted" or withdrawn to shore. Bridges of this design are considered obsolete because a relatively large piece of land has to be condemned - that is, left unusable - for their operation. However, such bridges are fairly simple to operate because of the relatively small amount of electrical and mechanical equipment needed to run them. There are 2 Retractile bridges under the control of the NYCDOT. 1. Borden Ave., a highway bridge over the Dutch Kill 2. Carroll St., a highway bridge over the Gowanus Canal Swing Span Typically, these are bridges supported on a center pier in the middle of a waterway. They are opened by rotating horizontally on wheels riding on a circular track. In this way, two channels are provided on either side of the bridge. A classic example of this type of structure is the bridge over the Harlem River at 207th Street (at right). Recent design trends, however have favored bridges which do not swing the full 90°. (As an example, see the Southwest Spokane Street Swing Bridge, in Seattle, WA.) Bridges of this type require waterways of considerable width; in addition, they are slow to operate and restrict the width of the channel. Because of this, they are rarely built today. There are 7 Swing Span bridges under the control of the NYCDOT. 1. 145th St., a highway bridge over the Harlem River 2. Macombs Dam, a highway bridge over the Harlem River 3. Madison Ave., a highway bridge over the Harlem River 4. Third Ave., a highway bridge over the Harlem River 5. W. 207th St., a highway bridge over the Harlem River 6. Willis Ave., a highway bridge over the Harlem River 7. Grand St., a highway bridge over the Newtown Creek Vertical Lift A vertical lift bridge is a movable bridge which carries roadways or walkways, and which can be raised and lowered like an elevator in a building. Vertical lift bridges are raised and lowered using supporting end cables that are attached to rotating drums in the towers on each side of the bridge. There are 4 Vertical Lift bridges under the control of the NYCDOT. 1. Roosevelt Is., a highway bridge over the East River (E. Channel) 2. Ninth St., a highway bridge over the Gowanus Canal 3. Broadway, a highway bridge over the Harlem River 4. Wards Is., a pedestrian bridge over the Harlem River