Measurement of a track position is carried out in successive measurement sections, wherein the relative track position is registered in each case with the aid of a long chord, formed by a laser beam, which serves as reference line of a measuring system. There are fault-sensing units in the belt, each comprising a conductive loop extending across the belt and a sensing circuit. The electrical distribution grid can have a plurality of spaced apart junction boxes each linked at least to a power source. Using the calorimetric value differences and the post-dry-down calorimetric values, device-dependent data are converted into colorimetric values, which represent pre-dry-down device-independent data.