Is a viaduct the same as a bridge?

Technically, a viaduct is a specific type of bridge. While a bridge spans a specific obstacle like a river, a viaduct is a long multi-span structure that carries the track over land or a valley.

Why are viaducts used instead of embankments?

Viaducts are used when an embankment would be too large, unstable, or expensive to build. They are also used when the space underneath needs to remain open for rivers, roads, or wildlife.

What defines a viaduct?

A viaduct is defined by having multiple short spans connecting a series of piers or arches, typically traversing a long distance over land rather than a single body of water.

Spanning the Gap: The Difference Between a Bridge and a Viaduct

While often used interchangeably, bridges and viaducts serve different structural roles. Discover the engineering differences between spanning a river and crossing a long valley.

December 9, 2025 12:15 pm

What is the Difference?

In railway engineering, the terms Bridge and Viaduct are often used loosely, but there is a distinct technical difference. The simplest rule of thumb is: “All viaducts are bridges, but not all bridges are viaducts.”

A Bridge is a general structure built to span a physical obstacle, such as a body of water, a valley, or a road.

A Viaduct is a specific type of bridge. It consists of a series of small spans connected to each other, supported by a succession of arches or piers. Viaducts are typically used to carry a railway (or road) over a long distance across dry land, such as a wide valley or an urban area, keeping the track level consistent.

Etymology and Function

The word “Viaduct” comes from the Latin via (road) and ducere (to lead). Unlike a standard bridge that might cross a river in one big leap, a viaduct “leads the road” over the landscape on stilts.

In the 19th century, railway engineers built massive brick or stone masonry viaducts to cross rolling hills. Building a solid earth embankment would have been too heavy or would have blocked the flow of water and traffic below. A viaduct allows the track to stay high and level while leaving the ground underneath open.

Comparison: Bridge vs. Viaduct

To distinguish between the two, we look at the structure and the obstacle being crossed.

Feature	Standard Bridge	Viaduct
Primary Obstacle	River, Road, Canyon	Wide Valley, Lowland, Urban Area
Structure	Few large spans (Long distance between supports)	Many short, repetitive spans (Short distance between supports)
Support System	Abutments and few piers	Multiple piers or arches in a series
Typical Design	Suspension, Truss, Cable-stayed	Arch, Beam, Deck-on-piers

Why Viaducts are Essential for Railways

Trains cannot handle steep gradients. While a car can drive down into a valley and back up, a train requires a flat line. Viaducts act as “artificial ground,” maintaining the high altitude of the track for kilometers. The iconic Glenfinnan Viaduct in Scotland (made famous by Harry Potter) is a classic example of using multiple masonry arches to curve around a valley while keeping the track perfectly flat.