An access module for a modular access structure, said access module comprising: a longitudinally and vertically extending first frame having a longitudinally extending upper chord and a longitudinally extending lower chord ; a longitudinally and vertically extending second frame having a longitudinally extending upper chord and a longitudinally extending lower chord , said second frame laterally opposing said first frame ; a deformable lower support structure laterally extending between said first and second frames , said lower support structure including a deck spanning a longitudinal length of said access module ; and a deformable upper support structure laterally extending between said first and second frames , said upper support structure being spaced above said deck to define an access passage extending along a length of said access module between said deck , said upper support structure and said first and second frames ; wherein said access module is configurable by deformation of said lower and upper support structures between an extended configuration in which said first and second frames are spaced apart a first distance and said deck is generally horizontal and a collapsed configuration in which a distance between said first and second frames is less than said first distance; further wherein said access module is adapted to be fastened end to end to a second access module to form a modular access structure with an access passage extending along a length of the modular access structure, each of said lower chords being adapted to be fastened end to end to a corresponding lower chord of the second access module to form a single load bearing elongate lower chord assembly. a longitudinally and vertically extending first frame having a longitudinally extending upper chord and a longitudinally extending lower chord ; a longitudinally and vertically extending second frame having a longitudinally extending upper chord and a longitudinally extending lower chord , said second frame laterally opposing said first frame ; a deformable lower support structure laterally extending between said first and second frames , said lower support structure including a deck spanning a longitudinal length of said access module ; and a deformable upper support structure laterally extending between said first and second frames , said upper support structure being spaced above said deck to define an access passage extending along a length of said access module between said deck , said upper support structure and said first and second frames ; wherein said access module is configurable by deformation of said lower and upper support structures between an extended configuration in which said first and second frames are spaced apart a first distance and said deck is generally horizontal and a collapsed configuration in which a distance between said first and second frames is less than said first distance; further wherein said access module is adapted to be fastened end to end to a second access module to form a modular access structure with an access passage extending along a length of the modular access structure, each of said lower chords being adapted to be fastened end to end to a corresponding lower chord of the second access module to form a single load bearing elongate lower chord assembly. <EOS>