How does machine surveying improve the maintenance of railway tracks?

Railways are perhaps the area where machine measurement has made the biggest impact. The Swedish Transport Administration already uses specially equipped measurement vehicles to regularly measure track positions and overhead lines in order to obtain data for maintenance and ensure the safety of the facility. Here at Atritecs, we contribute with more flexible, modular systems to be able to offer measurement of railway tracks even outside the regular measurement wagon schedule, as well as for project and construction purposes. The following main applications can be performed: 

• Track position measurement: Using inertial navigation, GNSS and laser scanning, the geometric position of the track is continuously measured. Parameters such as track gauge, superelevation, gradients, horizontal and vertical curves and any track twist or settlement are recorded with millimetre precision. The data is compared against applicable tolerances to find deviations. This is invaluable for planning track alignment and maintenance efforts. Previously, manual measurement was needed on site, but machine measurement provides a loaded track position in normal operation, which better corresponds to real stresses on the track. By collecting track data more frequently and in more detail, maintenance can be more proactive. Research in digital twins for railways shows that if all track data is available digitally, it is possible to monitor wear along each part of the track in real time and predict when measures are needed. 

• Contact line measurement: Laser scanning and high-resolution cameras can measure the distance from track to contact wire (wire height) and its lateral displacement (sway) along the entire line. This is critical for the safety of electric operation – incorrect height or waypoint can lead to wear on pantographs or contact wire. With machine measurement, you get a complete profile of the contact wire's position in height and sideways, even under bridges and in tight curves, and can adjust deviations more quickly. The measuring vehicle 360 cameras also visually document the condition of the line (e.g., if there are hanging cables, approaching vegetation, etc.). All data is georeferenced so that problem areas can be easily re-located for action. 

• Ballast measurement: The ballast (the macadam under and around the sleepers) can be inspected both from above and from the inside with sensors. The 3D laser scanner records the ballast profile – you can see where ballast is missing or has too high a profile that prevents drainage. Ground penetrating radar (GPR) can also detect hidden problems below the surface, such as fouled ballast, settlement problems in the subsoil or water pockets. These things are not visible to the naked eye but can lead to track errors if they are not addressed. By integrating GPR data with other measurements (track position, profile), you get a complete picture of the status of the ballast – both its external profile and internal condition. Such integrated inspection makes it possible, for example, to detect incipient ”mud holes” (ballast that has broken down to clay) and plan improved drainage before safety is affected. 

• Documentation of wear: High-resolution line laser scanners can measure the cross-section of the rail head on the fly, making it possible to map rail wear (reduced profile height or width) over long distances. Other components – such as switch tongues, rail joints or concrete sleepers – can also be documented to see cracks or abrasion. IR cameras can be used to detect thermal anomalies, such as overheated bearings in passing trains (hotbox detection) or hot running in electrical components along the track. By collecting and comparing wear data over time, it is possible to optimize replacement intervals for rails and other components. For example, a digital twin model of the track can be updated with traffic data and wear history to predict where wear will occur next and maintenance can be planned accordingly. 

• Digital site visits and mapping: All collected data (point clouds, panoramic images, video clips) can be used to conduct a virtual site visit. Engineers can “move” along the track in a 360-degree view at their computers, zoom in on details and even extract coordinates and measurements directly from the point cloud. This is particularly valuable in hard-to-reach environments such as tunnels, bridges or railway yards with heavy traffic – it reduces the need to send personnel out multiple times for measurement or inspection. For example, Atritec provides the Infra 360 Panorama service where customers can navigate measured environments in the browser. Such digital twins of the infrastructure create a completely new overview and make it possible to study a site in advance before work. Being able to get data without being out in the field saves both time and increases safety. 

In summary, machine-based railway surveying means that the condition of the track and its surroundings can be inventoried much more quickly than through traditional methods. Atritec has laser scanned over 6,000 km of railway tracks in 2023, which corresponds to more than half of the Swedish railway network, and this data set can now be used by the Swedish Transport Administration and contractors to plan maintenance more accurately. The accuracy of the measurements (relatively <1 mm) means that the results can be used for construction documents – for example, when designing track adjustments or yard renovations, where you need exact coordinates at the existing location to draw new drawings. By having fresh digital models, many jobs can also be prepared without the track owner first having to send out personnel for supplementary measurements, which saves time, money and avoids unnecessary occupation of tracks.