Ascertainment of the available reserve space for track elevation

Over time, the tracks of railway lines on ballast beds can suffer local displacements and deformations. This causes unwanted juddering of passing trains, which both reduces passenger comfort and can lead to more intense wear and tear. As a result, the lines must be maintained from time to time.

This is done by elevating and/or laterally displacing the track and filling the resulting space under the sleepers with ballast. This process, known as packing, is performed using modern machines at a rate of up to two kilometres per hour.

Packing generally has the effect of elevating the track. It is therefore important to know whether there is any remaining clearance for further track maintenance.