a vibration system that fits on top of a conventional truss with minimal alteration . the system comprises a propulsion assembly powering a vibration assembly . the propulsion assembly comprises two parallel rails forming a lateral path between truss ends and supporting a mobile carriage . each rail comprises abutting segments coextensively surmounting the truss . each segment attaches at respective truss cross - beams to define a continuous runway for carriage movement . each segment also defines a channel for a chain rack anchored at opposite truss ends . the carriage comprises an undercarriage supporting an offset platform . the undercarriage comprises a rail - spanning frame with supporting runway tracking wheels . a motor propels the carriage by turning an axle with terminal pinions entrained about the rack . the offset counterbalances the vibration assembly to reduce torsion . a coupling hitch protrudes from the platform opposite the offset to support the vibration assembly . the vibration assembly comprises an elevator that vertically displaces a gang of vibrators between deployed and retracted positions . the elevator comprises a hydraulic cylinder coaxially centered between two sleeves with sliding arms that couple the gang to the elevator . the gang comprises a plurality of quick - coupling pendulous vibrators across the truss front . a motor drives multiple vibrators via a split axle connected to several gearboxes in series . when deployed , the vibrator tip thrusts into the concrete and undulates rapidly for a selected time . afterwards , the vibrators retract and the carriage moves to an adjacent vibrated sector of concrete until completely traversing the truss . they system may operate automatically or manually .