A method for spans launched, as self-supporting bridge beams, approximately horizontally from support structure to successive support structure without significant temporary false work or scaffolding between permanent support structures. Bridge spans assembled atop previously constructed roadbed are launched individually onto supporting structures or columns spaced at span widths beyond said roadbed. 3 individual spans are placed or assembled with a longitudinal girder into a unit atop the roadbed surface, the assembly becoming a launching truss. Load moving air cushion pallets are placed upon the roadbed beneath and before the 3 spans. The launching truss moves forward one span length beyond the roadbed end placing one span and assembled girder in cantilever. That span is disconnected from the truss and emplaced upon supporting structures, at eventual roadbed level, beyond the previously constructed roadbed. Repeated, the process completes the bridge.