Mobile work station

A work station for a bridge comprising:

• an envelope (20) having a top section (30), a bottom section (31), first (32) and second (33) end sections, and first (34) and second (35) side sections spaced apart from the bridge by a distance sufficient to permit workers to access all surfaces of the bridge, wherein each said section is constructed of a material suitable to shelter workers and to contain debris, each section being suspended between a supply means and a take-up means (40--40' to 45--45') that permit the sections to be unfuried to construct the envelope or furied to take down the envelope;
• a plurality of support means (63) to suspend the supply means and take-up means for said sections about the bridge, said support means being mounted in a first motive means (21) adapted to be mounted on the bridge to permit the envelope to be repositioned from time to time;
• scaffolding means (80-81) to support workers within the envelope in close proximity to surfaces of the structure, said scaffolding means being suspended by cables connected to a second motive means to permit a vertical degree of freedom, said cables being mounted on a third motive means on a transverse beam (84) for a lateral degree of freedom and each said beam being mounted on a fourth motive means to permit a longitudinal degree of freedom of movement;
• a passage from the first end to the second end within the envelope to permit the passage of traffic during maintenance operations.