The response of a railway track structure to applied train loading depends on the complex interaction of its components - the super structure comprising the rails, fasteners and the sleepers and the substructure consisting of the ballast, subballast (if any) and the subgrade. The horizontal and vertical deformations of the substructure induce deviations in the horizontal alignment and vertical profile of the track from the designed geometry. Such track roughness affects riding quality and also results in increased dynamic loads which in turn leads to further deterioration of the track geometry and increased wear and tear.  Such problems necessitate frequent track maintenance (packing) and sometimes speed restrictions also, thereby affecting the cost and efficiency of operations.

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