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 (100, 200), 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 (100, 200), 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 (100, 200); wherein said access module is configurable by deformation of said lower and upper support structures (300, 400) between an extended configuration in which said first and second frames (100, 200) 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 (100, 200) 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 (120, 220) 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 (100, 200), 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 (100, 200), 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 (100, 200); wherein said access module is configurable by deformation of said lower and upper support structures (300, 400) between an extended configuration in which said first and second frames (100, 200) 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 (100, 200) 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 (120, 220) 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.