Track geometry measurements are widely used for describing track quality. However, derailments and track deterioration are caused by forces arising in vehicle-track system. This research focuses on two types of vehicle response. Firstly, the inf luence of the longitudinal level irregularities on the vertical wheel-rail forces was examined. Secondly, the correlation between the lateral axle box acceleration and the cross level irregularities was investigated. Track geometry and vehicle response data were acquired simultaneously by a track recording car, formed from a passenger car, at various speeds up to 130 km/h. Vehicle-track forces were calculated based on accelerometers mounted on the car body, bogies and axle boxes, considering mass and moment of inertia. Non-linear regressions resulted in vertical vehicle-track force estimation functions. It was proven that the use of second spatial derivatives of the longitudinal level gave a better estimation than the use of reference TQIs according to European Standard EN 13848-6. A linear relationship was found between the speed and standard deviation of vertical vehicle-track forces. On straight sections with constant speed, correlation coefficients of around 0.8 were found between second spatial derivatives of cross level and lateral axle box acceleration.

Track geometry measurements are essential for day-to-day activities of railway maintenance and play an important role in vehicle-track simulations. The generally applied forms of longitudinal level and alignment recordings do not reflect the real shape of the track. Both the versine measurement method and the band-pass filters according to European regulation cause significant amplitude modification and pattern change. In addition, the distortion behavior of repetitive and isolated defects is fundamentally different. In this contribution, simulated measurements of various reference shapes, which represent repetitive and isolated track deformations, were investigated. Comprehensive functions for amplitude change and for other distortion factors were developed with analytical and numerical methods. For chord measurements, rules were found for zero points and distortion-free ranges. Regarding the standardized filters, a significant amplitude reduction of isolated defects was observed in all wavelength ranges. Since derailment and track degradation depend not only on the amplitude of the defect, also the derivatives of the original and filtered forms of reference shapes were investigated and, as a new approach, the defect features called 'hypothetical additional force', 'speed of hypothetical wheel lift-off', 'hypothetical deterioration impulse' and 'hypothetical deterioration energy' were introduced.