Composite materials offer bridge designers the advantages of high stiffness-to-weight and high strength-toweight ratios when compared to conventional construction materials such as steel and reinforced concrete. FRP can be preformed into complete structural units, thus reducing construction time. In addition, FRPs have excellent corrosion resistance particularly against de-icing salts.

Bridges are one of the highest forms of civil engineering - few other structures command the same combination of functionality and visual impact. Major projects both in the UK and abroad have been quite regular events over the past decades (e.g. Humber Bridge, Second Severn Crossing). In recent years there has been something of a renaissance in the art of medium-span bridge design, particularly of footbridges. One catalyst for this has been the 27 bridges funded by the Millennium Commission with notable examples being The River Lune, Shanks, Lowry and Gateshead Millennium Bridges. A feature common to all of these is the slenderness of the design and use of steel (either stainless or non-corroding Cor-Ten). To a certain extent the cost of materials and complexity of design have taken a back seat to aesthetics and innovation. The most extreme example of this is the Arup/Lord Foster "Blade of Light" across the Thames.

For vehicle carrying bridges in the UK, particularly across motorways, reinforced concrete or steel is the norm. FRP materials may have particular applications in deck replacement (see Decks), where corrosion resistance and speed of installation are important, and in bridge enclosure systems where they provide environmental protection (see Bridge enclosure systems). One highly specialist application for FRP has been air-transportable military bridges. In countries such as Canada, North America, Norway, Sweden and Denmark there have been major programmes developing the use of timber as a renewable resource for footbridges and medium span vehicle bridges. Particular developments have been the stress laminated timber deck and composite concrete/timber deck (also featuring the use of non-ferrous FRP reinforcement), and carbon fibre strengthening of glulam and other engineered wood (see Strengthening). Timber has an obvious aesthetic and environmental appeal over FRP which is hard to ignore, and perhaps will be the major competitor for footbridges particularly in parkland or the countryside. Interestingly, both timber and FRP suffer from the same prejudices of poor fire resistance, durability and vandal resistance. FRP offers bridge designers an alternative material with excellent properties of high strength, stiffness and good durability in complete
structural units. The challenge will be to use FRPs in aesthetically pleasing designs, and in
combination with traditional materials such as timber (for example, as parapets or decking).