The ballastless track is nowadays the most popular railway system due to the required low number of maintenance operations and costs, despite the high investment. The gradual change from ballasted to ballastless tracks has been occurring in Asia, but also in Europe, increasing the number of transition zones. The transition zones are a special area of the railway networks where there is an accelerated process of track degradation, which is a major concern of the railway infrastructure managers. Thus, the accurate prediction of the short- and long-term performance of ballastless tracks in transition zones is an important topic in the current paradigm of building/rehabilitating high-speed lines. This work purposes the development of an advanced 3D model to study the global performance of a ballastless track in an embankment–tunnel transition zone considering the influence of the train speed (220, 360, 500, and 600 km/h). Moreover, a mitigation measure is also adopted to reduce the stress and displacements levels of the track in the transition. A resilient mat placed in the tunnel and embankment aims to soften the transition. The behaviour of the track with the resilient mat is evaluated considering the influence of the train speed, with special attention regarding the critical speed. The used methodology is a novel and hybrid approach that allows including short-term and long-term performance, through the development of a powerful 3D model combined with the implementation of a calibrated empirical permanent deformation model.

Rail vehicles generate huge longitudinal impact loads in collisions. If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body, the risk of car body structure damage and train derailment will increase. Herein, a four-stage rigid–flexible coupling finite element model of the coupler is established considering the coupler buckling load. The influence of the coupler buckling load on the train longitudinal–vertical–horizontal buckling behavior was studied, and the mechanism of the train horizontal buckling instability in train collisions was revealed. Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically. The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision. If the strength of the two sides of the car body structure in the lateral direction is asymmetrical, the deformation on the weaker side will be larger, and the end of the car body will begin to deflect under the action of the coupler force, which in turn causes the train to undergo sawtooth buckling.

Rolling stock manufacturers are finding structural solutions to reduce power required by the vehicles, and the lightweight design of the car body represents a possible solution. Optimization processes and innovative materials can be combined in order to achieve this goal. In this framework, we propose the redesign and optimization process of the car body roof for a light rail vehicle, introducing a sandwich structure. Bonded joint was used as a fastening system. The project was carried out on a single car of a modern tram platform. This preliminary numerical work was developed in two main steps: redesign of the car body structure and optimization of the innovated system. Objective of the process was the mass reduction of the whole metallic structure, while the constraint condition was imposed on the first frequency of vibration of the system. The effect of introducing a sandwich panel within the roof assembly was evaluated, focusing on the mechanical and dynamic performances of the whole car body. A mass saving of 63% on the optimized components was achieved, corresponding to a 7.6% if compared to the complete car body shell. In addition, a positive increasing of 17.7% on the first frequency of vibration was observed. Encouraging results have been achieved in terms of weight reduction and mechanical behaviour of the innovated car body.

Train timetables and operations are defined by the train running time in sections, dwell time at stations, and headways between trains. Accurate estimation of these factors is essential to decision-making for train delay reduction, train dispatching, and station capacity estimation. In the present study, we aim to propose a train dwell time model based on an averaging mechanism and dynamic updating to address the challenges in the train dwell time prediction problem (e.g., dynamics over time, heavy-tailed distribution of data, and spatiotemporal relationships of factors) for real-time train dispatching. The averaging mechanism in the present study is based on multiple state-of-the-art base predictors, enabling the proposed model to integrate the advantages of the base predictors in addressing the challenges in terms of data attributes and data distributions. Then, considering the influence of passenger flow on train dwell time, we use a dynamic updating method based on exponential smoothing to improve the performance of the proposed method by considering the real-time passenger amount fluctuations (e.g., passenger soars in peak hours or passenger plunges during regular periods). We conduct experiments with the train operation data and passenger flow data from the Chinese high-speed railway line. The results show that due to the advantages over the base predictors, the averaging mechanism can more accurately predict the dwell time at stations than its counterparts for different prediction horizons regarding predictive errors and variances. Further, the experimental results show that dynamic smoothing can significantly improve the accuracy of the proposed model during passenger amount changes, i.e., 15.4% and 15.5% corresponding to the mean absolute error and root mean square error, respectively. Based on the proposed predictor, a feature importance analysis shows that the planned dwell time and arrival delay are the two most important factors to dwell time. However, planned time has positive influences, whereas arrival delay has negative influences.

Cyclic load is widely adopted in laboratory to simulate the effect of train load on ballast bed. The effectiveness of such load equivalence is usually testified by having similar results of key concerns of ballast bed, such as deformation or stiffness, while the consistency of particle scale characteristics under two loading patterns is rarely examined, which is insufficient to well-understand and use the load simplification. In this study, a previous laboratory model test of ballast bed under cyclic load is rebuilt using 3D discrete element method (DEM), which is validated by dynamic responses monitored by high-resolution sensors. Then, train load having the same magnitude and amplitude as the cyclic load is applied in the numerical model to obtain the statistical characteristics of inter-particle contact force and particle movements in ballast bed. The results show that particle scale responses under two loading patterns could have quite deviation, even when macro-scale responses of ballast bed under two loading patterns are very close. This inconsistency indicates that the application scale of the DEM model should not exceed the validation scale. Moreover, it is important to examine multiscale responses to validate the effectiveness of load simplification.

The CRTS II slab track, which is connected in a longitudinal direction, is one of the main ballastless tracks in China, with approximately 7365 km of operational track. Temperature loading is a very vital factor leading to slab track damages such as warping and cracking. While existing research on temperature distribution rests on either site tests in special environments or theoretical analysis, the long-term temperature field characteristics are not clear. Therefore, a long-term temperature field test for the CRTS II slab track on bridge-subgrade transition section was conducted to analyze the temperature field. A GA-BP (genetic algorithm optimized back propagation) neural network was trained on the test data to predict the temperature field. The vertical and lateral temperature distributions in four typical days were carried out. We found that the temperature along the track was distributed in a nonlinear manner. This was particularly distinct in the vertical direction for depths of less than 300 mm. The highest and lowest daily temperatures and the daily range of the temperature were analyzed. With the increasing depth, the daily highest temperatures and range of the temperature were smaller, the daily lowest temperatures were higher, and the time corresponding to this peak value appeared later in the day. Both the highest and lowest daily temperature could be predicted using the GA-BP neural network, though the accuracy in predicting the highest temperature was higher than that in predicting the lowest temperature.

The harmonics and resonance of traction power supply systems (TPSSs) aggravate the electromagnetic interference (EMI) to adjacent metallic pipelines (MPs), which has aroused widespread concern. In this paper, an evaluation method on pipeline interference voltage under harmonic induction is presented. The results show that the Carson integral formula is more accurate in calculating the mutual impedance at higher frequencies. Then, an integrated train–network–pipeline model is established to estimate the influences of harmonic distortion and resonance on an MP. It is revealed that the higher the harmonic current distortion rate of the traction load, the larger the interference voltage on an MP. Particularly, the interference voltage is amplified up to 7 times when the TPSS resonates, which is worthy of attention. In addition, the parameters that affect the variation and sensitivity of the interference voltage are studied, namely, the pipeline coating material, locomotive position, and soil resistivity, indicating that soil resistivity and 3PE (3-layer polyethylene) anticorrosive coating are more sensitive to harmonic induction. Field test results show that the harmonic distortion can make the interference voltage more serious, and the protective measures are optimized.