The traditional method of analysing track geometry measurements is based on comparisons (for various cord lengths) of the maximum amplitude of each measuring signal with a speed dependent limit value.
The disadvantage is that it does not account for multiple defects on the same locations (and their accumulated impact), nor considers the influence of driving direction, or the effect of the shape of the defect on the dynamic loads of the track.
This makes it very dificult to preserve safety, plan efficient maintenance and avoid unnecessary speed restrictions.
PUPIL's data-driven model
PUPIL is a sophisticated software tool that simulates the dynamic interaction between the rolling stock and infrastructure (known as vehicle response analyses). It uses a digital twin of the vehicle types running on the network and the track condition data that was captured by measurement vehicles.
The tool examines a selection of vehicle types typical to the track section across a range of variables such as differing speeds and loading conditions. The track geometry is evaluated using calculated vehicle reactions and provides an assessment on track forces, Y/Q safety against derailment coefficient and car body accelerations.
The most critical configuration determines the safety factor relative to the limit values from euronorm EN14363.
The analyses are undertaken for speeds up to the local maximum speed. If a safety limit is exceeded, PUPIL provides the safe speed where all vehicle responses are still within the limits.
PUPIL can also provide analysis of the causes of exceedances to help plan corrective maintenance works. For example, its analysis can help establish if an exceedance on maximum lateral track force could have originated from an alignment defect 30 meters back.