A stressed ribbon bridge (also stress-ribbon bridge or catenary bridge) is a tension structure similar in many ways to a simple suspension bridge. The suspension cables are embedded in the deck, which follows a catenary arc between supports. As with a simple suspension bridge, the weight is taken by the suspension cables, but unlike the simple span, the deck or ribbon is stressed in compression, which adds to the stiffness of the structure (simple suspension spans tend to sway and bounce). The supports in turn sustain upward-thrusting arcs that allow the grade to be changed between spans (where multiple spans are used). Such bridges are typically made from concrete reinforced by steel tensioning cables. Where such bridges carry vehicle traffic, a certain degree of stiffness is required to prevent excessive flexure of the structure, obtained by stressing the concrete in compression.