Drainage structure which facilitates a communication pathway to carry road or railway traffic across an obstacle or depression with or without water, is called a bridge.

The route of communication can be railways, roadways, cycle tracks, sidewalks, or a combination of both, and the obstacle can be in the form of a river, stream, valley, channel, road, railway track etc.

Types of Bridge by Size
1- Minor Bridge: Minor bridge are the bridge having total span length greater than 6 m & less than 60 m.

2-Major Bridge: Major bridge are the bridge having total span length greater than 60 m.

c. Long Span Bridge: Long span bridge are the bridge having the main span length more than 120 m.

Classification of bridges by structural system

1- Truss Bridges
2- Suspension Bridges
3- Beam Bridges
4- Cable-stayed Bridges
5- Cantilever Bridges
6- Arch Bridges

Different types of materials like stone, brick, timber, steel, concrete, composite, aluminium and fibre are used to construct a bridge.


Culvert are the small bridge having total length of 6 m or less between the faces of abutments. This type culvert bridge are permanent drainage structures which are mainly made to carry roadway or railway track over small streams or canals.

Types of culvert

1- Pipe culvert (single or multiple)

2- Pipe-Arch culvert (single or multiple)

3- Box culvert (single or multiple)

4- Arch culvert

5- Bridge culvert

6- Metal box culvert

When is a culvert used in construction?

When water needs to be conveyed through a pipe or channel. Choosing the size and type of culvert (pipe, box or arch) depends on a number of factors including the amount of water flowing.

Difference Between Bridge and Culvert
Bridge Culvert
1 A bridge is a passage of transportation (for people or vehicles) over a large body of water or physical obstruction. A culvert is generally a tunnel-like structure that allows water to pass under a roadway or railway.
2 The basic components of a bridge are superstructure (supports load), substructure (transfers load to foundation soil) and deck (transfers surface load to other components). The components of a culvert are comparatively simpler and include concrete boxes or cells (single or multiple), pipes, a top deck or slab and supporting parts.
3 Bridges are constructed at a height more than 20 feet. Culverts are built at less than 20 feet high over the obstruction.
4 A bridge spans from 6 meters (minor bridges) to more than 120 meters. The length of culverts is typically not more than 6 meters.
5 Piers and abutments are the supporting structures of a bridge. Culverts are usually embedded in the soil which bears the major portion of the culvert load.
6 A bridge contains no floor. A culvert is an enveloping structure that consists of two sides, a roof, and a floor.
7 The construction of a strong and deep foundation is very important in building a bridge. The foundation along the entire breadth supports the bridge. No deep foundation is required for a culvert.
8 A bridge is usually a linear and straight passage. Culverts are totally enclosed structures that can be semi-circular, rectangular, elliptical or pear-shaped.
9 The structure and design of a bridge are elaborate and complex, hence its construction requires a substantial budget. The construction of a culvert can be done with a low budget.
10 Bridges are usually constructed at the site or pre-constructed in smaller parts. Culverts can be pre-constructed or built at the site (in situ culverts).
11 Construction of bridges generally requires a lot of time and manpower. Culverts are simpler in structure and design, so it can be constructed with less time and labor.
12 Bridges provide an easier route of transportation that saves time and reduces distance. Culverts prevent water logging, flood, and erosion, and allows water to flow its natural course under a roadway or railway.
13 A bridge is built over a body of water that is large and has variable flow. A culvert is constructed when water needs to be conveyed through tunnels or channels under a roadway.
14 Bridges can withstand heavy and speeding vehicles. Some culverts, like box culverts, have sharp corners that are unsuitable for high-velocity vehicles.
15 The only way of transportation is over the deck of the bridge. A culvert can be constructed to accommodate roadways both over and under the deck (e.g. a culvert built over another road or railway).

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