A culvert is a concrete tube profile that is used as a connection between two waterways under a paving (road). A culvert bridge can contain a pipe culvert, but this is not necessary. Short T-girders, amplitude girders and P-plates can also form the basis for a culvert bridge. What makes it a culvert bridge?
Much depends on the structure of the front walls. The relatively enclosed nature of the water passageway is characteristic of a culvert bridge. This opening can be round or rectangular, but it always has modest dimensions. The presence of voluminous abutment pier boxes or slope pieces, in facing concrete or otherwise, or with brickwork, can contribute to this. The variety of bridge main walls is endless. The finish on the bridge is also boundless and can be supplemented by a railing of choice.
The majority of culvert bridges only have a single opening so that no intermediate supports are needed. This is not, however, a necessity. There are also culvert bridges with two or more passageways. The width can be varied by simply increasing the length of the culvert and moving the front walls. The span can also be freely selected.
Culvert bridges often function as traffic bridges (read: main access) to a specific area, a residential area for example. They mark the boundaries of the functional area while other bridges are used inside the area.
In summary, there are a number of characteristics that together embody the term culvert bridge. None of these are essential per se, but the combination is characteristic of a culvert bridge.