These measurements have been carried out by means of laser systems by institutes in the research sector (e.g. TU Berlin) for quite some time. For this, the lasers were arranged in free space profile, so that measuring was carried out diagonally to the side of the rail. This positioning required a later correction of the measuring values due to the individual movement of the measuring vehicle.
Just recently, a special sensor for track-width measuring has become available. Here, the laser beam within the sensor is redirected twice, so that vertical measuring at the measuring point, stipulated in the norm, is possible at the wheel head. The sensor has been positioned in such a way in the shadow of the wheel that it is also possible to pass through point mechanisms without any lifting of the measuring system. The sensor is waterproof, and in case of contamination, the optical installation is cleaned automatically by a cleaning system.
Comparative measurements with contact systems (max. 120 km/h) have generated absolutely identical, reproducible measuring values. The sensor can be operated at a speed of up to 250 km/h