**3.2 Structures and functions**

Depending on the span to be covered, the traffic flow, the availability of materials and labor, the designer will define the geometry of the bridge. Most of the bridges have short spans and use girders of reinforced concrete, pre-stressed concrete or structural steel. Bridges with intermediate spans use trusses and arches. For very large spans, suspended bridges are the best option.

All types of bridges must have the following qualities:

