Abstract: The bridge includes a plurality of foldable portions or modules (M) interconnectible releasably in sequence longitudinally. Each module (M) includes a central deck member (9) and two lateral deck members (10, 11) articulated to opposite sides of the central deck member (9). Respective longitudinal beams (13-16) extend from the lower faces of the lateral deck members (10, 11) and, together with the homologous beams of the other modules (M), constitute the load-bearing trusses of the bridge in its condition of use.Conveniently, the bridge is constructed by a method of assembly which provides for the use of a load-bearing assembly structure or forestarling (S). This load-bearing assembly structure (S) is assembled in a position of assembly on a first side (B.sub.1) of the gap (R) to be spanned by the bridge and is then advanced until it reaches the other side (B.sub.2) of the gap.