A round, corrugated drainpipe, normally 15 or 18 inches in diameter, that is installed beneath a driveway parallel to and near the street.
A culvert is a structure that allows water to flow under a road, railroad, trail, or similar obstruction from one side to the other side. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom, the word can also be used for a longer artificially buried watercourse. A structure that carries water above land is known as an aqueduct.
Culverts are commonly used both as cross-drains for ditch relief and to pass water under a road at natural drainage and stream crossings. A culvert may be a bridge-like structure designed to allow vehicle or pedestrian traffic to cross over the waterway while allowing adequate passage for the water. Culverts come in many sizes and shapes including round, elliptical, flat-bottomed, pear-shaped, and box-like constructions. The culvert type and shape selection is based on a number of factors including requirements for hydraulic performance, limitation on upstream water surface elevation, and roadway embankment height.
If the span of crossing is greater than 12 feet (3.7 m), the structure is termed a bridge.
The process of removing culverts, which is becoming increasingly prevalent, is known as daylighting. In the UK, the practice is also known as deculverting.