Abstract: A suspension bridge has a first deck supported from a pair of suspension cables by hangers and a second deck independently supported from a pair of suspension cables by hangers. The two parallel decks are separated by a gap whose width is not less than that of either of the decks and is preferably three or more times the width of a deck. The decks are joined at intervals along their length by stiff transverse girders 22 and intervening diagonal shear braces so that the two decks behave essentially as a single rigid body in regard to torsional movement. This results in very high aerodynamic damping of both torsional and bending modes of oscillation.