Caltrans - Types of Structures
Sometimes the search for definitions goes astray. These definitions are not being used on this website. The terms used by the California Department of Transportation tend to be rather specific...maybe a bit too bureaucratic to be useful.
KINDS OF STRUCTURES (Caltrans)
Structures are named in accordance with the kind of facility they provide. To determine these names place yourself on the major facility and describe the structure from that position. Major facilities rank in the following order: (1) railroads, (2) highways, (3) county roads or city streets, (4) pedestrian walkways, cattle trails, etc.
Bridge -- The term "bridge" is usually reserved for structures over water courses.
Overhead -- A structure carrying a highway over a railroad is called an overhead.
Underpass -- A stucture which provides for passage of a highway under a railroad is an underpass.
Overcrossing -- A structure carrying a county road or a city street over a state highway is an overcrossing.
Undercrossing -- A structure which provides for passage of a county road or city street under a state highway is an undercrossing.
Separation -- A grade separation of two state highways is called a separation.
Interchange -- The group of ramps and structures required to provide connections for traffic between intersecting roadways is called an interchange.
Viaduct -- A structure of some length carrying a state highway over streets, railroads, or other various features is called a viaduct.
Tunnel -- A structure carrrying a state highway through a hill or mountain is called a tunnel.
Pedestrian Overcrossing -- A structure carrying a pedestrian walkway over a highway is a pedestrian overcrossing.
Pedestrian Undercrossing -- A structure which provides for passage of a pedestrian walkway under a highway is a pedestrian undercrossing.
Miscellaneous Structures -- Structures other than those described above are given a descriptive title such as Equestrian Overcrossing, Equestrian Tunnel, Cattlepass, Pipeline Overcrossing and Conveyor Belt Overcrossing.
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California Dept. of Transportation "Bridge Design Aids", February 1990, page 10-35