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  The many types of fixed or non-movable bridges are often classified according to their span, the materials they are constructed from, the placement of the travel surface in relation to the structure, and the form or shape that the structure takes. What form a bridge will take and how it will be constructed is largely determined by the obstacle it must cross and balancing engineering factors such as cost of materials.
  
  

Girder

• Girder bridges are made of beams called girders, the ends of which rest on piers or abutments. They are typically made from reinforced concrete or metal. Deck beam and deck plate girder configurations feature cross-bracing between the beams. Pony plate girders use knee braces instead. Some girder bridges have haunches at the supported ends to increase load capacity. Computer stress analysis has developed new designs that integrate superstructure and substructure in what are called rigid frame bridges.
  
  

Truss

• Truss bridges are supported by frameworks called trusses, which are comprise of beams arranged in triangular shapes. In a deck configuration, traffic travels on top of the main structure. In a pony configuration, traffic travels between parallel superstructures which are not cross-braced at the top. Lastly, in a through configuration, traffic travels through the superstructure, which is cross-braced above and below the traffic.
  
  

Cantilever

• A cantilever is a structural member which projects beyond its support and is supported at only one end. A cantilever bridge can be made from trusses, girders, or beams using this concept. The classic cantilever design is the "through truss", which extends above the deck. Some have trusses which extend both above and below the deck. Another variation of a cantilever is an arch atop vertical supports called spandrels, called a spandrel-braced cantilever.
  
  

Suspension

• Suspension bridges are the most recognizable and visually impressive bridges, featuring a roadway that hangs from steel cables supported by two high towers. Some such bridges are actually a hybrid design incorporating features of arch bridges, like the trussed-through arch and solid-ribbed arch types.