A structure carrying a roadway over the canal. Since they were built low to save money, a crew member sat up front in the boat and yelled to passengers, "Low bridge, everybody down," or they would be knocked off the boat.
Any structure carrying vehicles or pedestrians over an obstacle or depression. For ITD, it includes all overpasses, on-ramps, small bridges over streams, etc.
A structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening.