To put it simply, is the overhead bridge on the road. The main bridge has been made to resolve the cross-valley water or more of the traffic in order to transport or pedestrians on the bridge unimpeded. From the first or the most important function, the bridge should be specifically refer to cross-water line of empty road. Therefore, One Ancient book named "说文解字" comments: "with wooden cross water, this bridge also." Bridge of the original meaning of the note refers to the wood frame on the surface of the water channel.
Modern bridge in the city traffic to play an important role in the ground from the bridge (overpass), will not only help ease traffic jam, but also into a beautiful scenery of the modern city .
Chinese bridge is a living treasure of cultural relics, many valuable records.