Bridge enclosures are hybrid bridge systems and are an example of an application where composites on their own would not provide the most effective solution. A system has been developed for high performance bridges which feature the combination of several materials utilised in an optimum complementary manner. The hybrid system features a lightweight tubular steel space frame, steel cast nodes, an aerodynamically profiled FRP enclosure shell, and reinforced concrete roadway slab. The structure may be widened by additional space framing and post-tensioning cables. The space frame is enclosed by an aesthetic, aerodynamically profiled shell which provides permanent protection for the steelwork and safe access for inspection and maintenance of the superstructure and bearings.

Quality and overall efficiency are achieved by assembly of factory-built modular units on site, and the space frame affords savings in steel and fabrication content. For long span viaducts, whole span space frames up to 150m long may be erected in a single lift, and for cable-stayed bridges having main spans of up to 750m, SPACES decks can be economically constructed from large segments. For suspension bridges, the aerodynamic shape and good torsional stiffness of a SPACES deck make it an attractive system. On a smaller scale, the SPACES system is ideal for motorway widening over bridges. Slender decks can cross 60m carriageways in a single span. The enclosed space frame can be installed rapidly and the concrete deck slab added with minimum disruption to traffic. SPACES decks may also be used to construct high-speed and urban railway bridges which are quiet.