Box girder bridge

A box girder bridge is a bridge commonly used for roadway flyovers and for modern elevated structures of light rail transport. They may be fabricated from post-stressed concrete or sheet steel plate. If of concrete, they may be cast in place using falsework supports, removed after completion, or may be prefabricated (as is the steel plate type) in a fabrication yard, then transported and emplaced using cranes. The later method is often used in situation where access for construction is limited to times of light traffic, which may be detoured around the work area using only a limited number of lanes.