Railway Track Geometry Research Articles

A Novel Hybrid Method for Predicting Vertical Levelling Loss of Railway Track Geometry Under Dynamic Cyclic Loadings

With an emphasis on the integrated deterioration of railway track geometry and components, a new hybrid numerical-analytical method is proposed for the predictive analysis of track geometrical vertical levelling loss (VLL). In contrast to previous studies showing a dependency on the number of cycles, this research unprecedentedly incorporates the influence of operational, vehicle and track conditions. The numerical models are carried out using an explicit finite element (FE) package under cyclic loadings, and then, their outcomes are iteratively regressed by an analytical logarithmic function that accumulates permanent deformations in order to quantify VLL over a long term. The results are first compared with other previous studies, indicating a very good agreement with them. Then, field measurements have been used to further verify the results. In this study, parametric simulations are performed varying three key parameters: axle load, train velocity and ballast tangent stiffness. The parametric studies exhibit that the rate of VLL raises about 50% if the axle load increases only from 30 ton to 40 ton for a freight train running at 70 km/h on a stiffer ballast track. In contrast, for a 25-tonnes-axle-load train running from 60 km/h to 100 km/h on a similar track, the vertical levelling degradation reduces by approximately 20%. The main findings suggest that higher axle loads contribute significantly to the VLL due higher contact forces and, on the other hand, a lower train speed does not necessarily imply a low rate of VLL since the influence of train velocities on track geometry (VLL) is associated with the natural frequencies (or wavelengths) of the ballasted railway track. The insight demonstrates that the load frequencies play a key role on the deterioration of VLL.

Geogrid reinforcement of ballasted railway superstructure for stabilization of the railway track geometry – A case study

BackgroundThis article deals with a unique topic related to railway infrastructure, civil and geotechnical engineering, and modern materials. In the past 20–30 years, more and more synthetic materials have been applied in engineering and everyday life. Geogrid and geotextile products are adequate for substituting lacking abilities of the soils, and granular materials, mainly low tensile and shear strength, etc. This paper aims to introduce the result of the author's research dealing with investigating the behavior of geogrid-reinforced railway ballast based on a long-term field test in the busiest main railway line in Hungary. The duration of the test is more than eleven years. MethodsFive different types of geosynthetics were installed in the superstructure of the No. 1 main railway line (Kelenföld – Hegyeshalom state border) in Hungary in 2010. More than eleven years have elapsed since the installation. The experiences are formulated in this paper. Mathematical-statistical analysis was performed to compare the (sub)sections with each other and with the designated reference sections where no geogrids were applied. ResultsAs a result of the examination, the author summarized the main differences in the behavior of railway track geometry, and the geometrical deterioration rates, considering the different types of reinforcement products.

Verification of Satellite Railway Track Position Measurements Making Use of Standard Coordinate Determination Techniques

The article presents the results of satellite railway track position measurements performed by a multidisciplinary research team, the members of which represented Gdansk University of Technology and Gdynia Maritime University. Measuring methods are described which were used for reconstructing the railway track axis position and diagnosing railway track geometry deformations. As well as that, the description of the novel method developed by the authors to perform mobile GNSS measurements is included. The reported research aimed at assessing the uncertainty of railway track axis reconstruction making use of the dynamic GNSS method. To assess the applicability of this method, the obtained results were compared with those from the stationary measurement method used in railway business. The data used for comparison was recorded on the same railway track section during several measurement campaigns. In these campaigns, different types of GNSSs with different position recording frequencies (1–100 Hz) were used at different measurement speeds (5–70 km/h). The performed analysis has shown that the accuracy of railway track axis reconstruction making use of mobile GNSS measurements is sufficient for using this methodology in railway business.

Maintenance Decision Support Model for Railway Track Geometry Maintenance Planning Using Cost, Reliability, and Availability Factors: A Case Study

Determining the strategy and planning for maintenance operations on railway tracks is important given the increasing demand from both freight and passengers. An important prerequisite of maintenance planning is the ability to predict the overall and geometric conditions of the railway in the near future. It is, therefore, necessary to develop a degradation model and consider the effect of various maintenance operations using a recovery model. According to EN 13848-5, the alert limit (AL) can be used as an indicator to plan maintenance operations. The current paper benefits from this index as well as the effect of its changes on important parameters such as maintenance costs, availability, and reliability to present a maintenance decision support model. This model allows infrastructure managers to plan maintenance interventions under the conditions of their intended usage strategy. The results of this paper indicate that choosing suitable AL could affect total maintenance cost and availability by up to 57% and 33% respectively.

Advancing Railway Asset Management Using Track Geometry Deterioration Modeling Visualization

Railway tracks need to be monitored to ensure safe operations and cost-effective maintenance. The monitoring is commonly conducted using a track recording car that describes deviations from an ideal track geometry. Over time, the measurements provide time series data that can be used to model the observed track geometry deterioration process. However, without simplification, the modeling results are generally too complex to be utilized to their full extent in track asset management. Therefore, this study aimed to implement visualization techniques for track geometry deterioration modeling results analysis which benefit track asset management. The best practices on track geometry deterioration modeling were studied and applied to the track geometry history of a track section located in Finland. After testing the establishing modeling principles, proposals were made regarding the use of the results in practice. This paper presents visualization techniques that use the modeling results of individual cross-sections to generate information about longer sections of track and even whole rail networks. These visualizations digest the massive amount of information from the modeling and present it in an informative way for practitioners to utilize and benefit from. Thus, this study fills the gap between research and practice in railway track geometry deterioration modeling.

Исследование точности определения пространственного положения железнодорожного пути путеизмерительной тележкой Gedo

The implementation of the concept of integrated development of the scientific and technical project "Digital Railway" provides for the development of digital technologies in all areas of activity of JSC "Russian Railways", including the track economy. In order to monitor the current state of the tracks, digital models of the tracks are created and maintained at the level of modern requirements, used to collect, store and evaluate spatial data on the current state of the tracks and develop recommendations for the prevention and elimination of identified malfunctions. The most effective and universal means of controlling and straightening the track is the coordinate method based on a system of continuous coordinate-digital description of the track in a single coordinate system. Track measuring wagons widely used in the railway network do not allow obtaining the geometric parameters of the track in a single coordinate system. Because of this, in our country and in foreign countries, various track-measuring systems have been developed and are used, allowing to obtain the CMR in coordinates. Therefore, the purpose of theoretical and experimental research is to identify the accuracy of determining the geometric parameters of the railway track using the Gedo track measuring trolley. The method of determining the track geometry, technical characteristics and distinctive features of the Gedo track measuring trolley are considered. A program of experimental studies is described and comparative accuracy estimates of the railway track geometry determination by the geodetic method, using a Gedo track measuring trolley and a rail gauge template are given. It is shown that in connection with the transition of the railway industry to digital technologies for modeling infrastructure facilities, it is most expedient to use the Gedo track measuring trolley for monitoring the geometry of the railway track, which provide the required accuracy of determining the geometry of the track, productivity and obtaining the necessary information in a single coordinate system.

Railway track availability modelling with opportunistic maintenance practice

The geometry of railway track must be maintained within certain standards in order to provide a highly available network, as well as good ride comfort and safety for all rail users. Modelling is well utilised as part of asset management tools in exploring the effectiveness of different rail geometry maintenance strategies. By considering the rail route as an entire system – in contrast to a track section in isolation – a more effective maintenance strategy can be developed, including the deployment of opportunistic maintenance practice. This study presents a Coloured Petri Net model of railway track degradation, inspection, and maintenance planning and delivery, for an entire route of track sections. Opportunistic maintenance is introduced through a novel search transition function, which groups interventions based on local adjacency. Testing explores the availability and maintenance demands expected when following a series of different management strategies. This is extended to testing under heatwave conditions, a known disrupter to track geometry maintenance delivery. Simulation results show that in following an opportunistic strategy, greater availability can be achieved on the modelled rail line. Further, resilience to the heatwave disruptions can be achieved by selecting the correct maintenance strategy parameters. This asset management tool can provide guidance on management strategies for a full route of track sections as a combined system.

Novel Algorithm for Mutual Alignment of Railway Track Geometry Measurements

Track geometry measurements are regularly collected to monitor the condition of a railway network. To detect deterioration patterns and enable predictive maintenance, sequential measurement runs must be mutually aligned which has been proven a serious challenge. This paper presents a novel algorithm for mutual alignment of track geometry signal data. It resolves several previously intractable alignment problems: highly segmented data with variable sample rate, spatially correlated and uncorrelated measurement errors, convergence to true locations, and consistency over time. The algorithm adjusts spatial measurement errors by splitting signals in continuous segments. Re-sampled, error-corrected signals are mutually aligned using cross correlation, and this process is repeated until the mutual alignment meets a pre-defined precision threshold. Missing measurement values are handled by imputing an interpolated offset from nearby segments, ensuring that the signals remain continuous. By using weighted average offsets over all aligned signals, the law of large numbers guarantees convergence and consistency. The practical feasibility of the algorithm is demonstrated on empirical track geometry measurement data from the British railway network, owned and operated by Network Rail.

Quantifying the effect of freeze-thaw cycles on track surface deformation and degradation of railway track geometry; Case study

Freeze-thaw cycles (FTC) are known to have an effect on railway track stability, safety, and performance. FTC are expected to become more frequent in the future due to climate change. This paper presents the results of a field investigation in which the mechanism of FTC development within the track embankment and its effect on the performance of railway tracks including track surface deformation and track geometry degradation are studied. Field observations suggested that the frost depth within the track embankment is influenced by the freezing index and winter snow cover. They also showed that a warmer and drier winter leads to more intermittent FTC and even though the average frost heave is lower than for a colder winter, the frost heaves occurring at culvert locations creates a larger differential deformation and thus may lead to a worse operating condition. The comparison of geometry measurements before freezing and after thawing indicated that the track geometry is in poorer and rougher condition during springs that were preceded by increased FTC. It was also concluded that track in proximity to culverts suffered the highest geometry degradation. Overall, the limited field observations of this study suggest that future winters, mild with less precipitation and higher occurrence of FTC, may increase the rate of track deterioration and more maintenance will be required to keep track within safe limits.

Reducing the positional errors of railway track geometry measurements using alignment methods: A comparative case study

To predict the occurrence of geometry defects and to achieve a reliable maintenance strategy, accurate positioning of track geometry measurements is of great importance. This paper aims to reduce the positional errors in track geometry measurements by finding an efficient alignment method. Therefore, five alignment methods, i.e. the cross-correlation function, recursive alignment by fast Fourier transform, dynamic time warping, correlation optimized warping, and a combined method, were evaluated and compared concerning their ability to align the measurements precisely, keep the original shape of the measurements, and minimise the use of time and memory. Furthermore, the influence of choosing a proper reference dataset was investigated. A case study based on track geometry data from the Main Western Line in Sweden was conducted to implement and assess the methods. Findings revealed that the combined method could decrease the positional errors of single defects to below 0.25 m in 90% of the trials.

Innovative mobile method to determine railway track axis position in global coordinate system using position measurements performed with GNSS and fixed base of the measuring vehicle

The shape of the railway track axis and its position in the global coordinate system are essential when defining design parameters of the railway. Correct reconstruction of these quantities is vital for both verifying the compliance of real track parameters with the design and for diagnosing, as all track deformations can also be defined as deviations of real parameters from their design values. The measurements of quantities related to the railway track geometry can be divided into global and local ones. Global measurements determine the position of elements in the global system of geographic coordinates, while local measurements give relative positions of elements with respect to other elements (e.g. lateral inclination at a given kilometre of the railway track) or temporary deviation of parameters from their assumed value (e.g. various track deformations). Depending on the applied measuring method, either global or local parameters are determined, or both of them simultaneously. The article proposes an innovative method to determine the railway track axis position, which makes use of Global Navigation Satellite Systems (GNSS) receivers distributed in such a way as to form a geometric constraint called the fixed base. The analysis of theoretical properties and metrological attributes of the fixed base is presented. All theoretical analyses have been verified experimentally.

The impact of summer heatwaves on railway track geometry maintenance

Elevated summer temperatures are a disrupting factor on the rail network. Due to the risk of a track buckling under thermal expansion forces, geometry maintenance must be delayed during heatwaves, leading to an overall decreased network availability and reliability. Track asset management support tools are used to plan and schedule a variety of maintenance activities, with tamping and stoneblowing being the primary activities for geometry maintenance. No management tools seen in the literature consider the influences of weather on the scheduling and delivery of maintenance. This paper describes a Petri net modelling approach to railway track asset management. This is demonstrated to be a highly flexible method able to capture the complexities of degradation, inspection, and maintenance, and predict the evolution of track geometry quality over time. Different maintenance strategies are tested, varying the degradation thresholds, inspection intervals, policy decisions, and maintenance response times. Excessively hot weather is introduced as an inhibiting factor for all maintenance activities, resulting in extended periods where interventions are delayed. Simulation results show that frequent inspection and timely maintenance scheduling strategies could be followed to attain a highly performing and resilient track system. This asset management support tool could be added to the suite used by the rail industry, providing guidance on maintenance policy through a summer season where heatwave disruptions are expected.

Optimization of maintenance strategies for railway track-bed considering probabilistic degradation models and different reliability levels

An optimization-based maintenance scheduling framework is an essential tool to plan the necessary investment to maintain the required performance of a railway line. In the present study, a methodology is proposed to minimize the present value of the life cycle maintenance costs and maximize the life cycle quality level of the track-bed considering different levels of reliability. Probabilistic degradation models are developed for predicting the evolution of the railway track condition over time. Afterwards, a Genetic Algorithm based optimization procedure is applied for obtaining a set of optimal solutions taking into account several constrains. The proposed methodology is applied to an Italian railway track-line case study. The results show that it is possible to develop a decision support system to help railway managers to schedule railway track maintenance operations based on the optimal trade-off between maintenance costs and railway track geometry condition for different levels of reliability.

Self-Organized Model Fitting Method for Railway Structures Monitoring Using LiDAR Point Cloud

Mobile laser scanning (MLS) has been successfully used for infrastructure monitoring apt to its fine accuracy and higher point density, which is favorable for object reconstruction. The massive data size, computational time, wider spatial distribution and feature extraction become a challenging task for 3D point data processing with MLS point cloud receives from terrestrial structures such as buildings, roads and railway tracks. In this paper, we propose a new approach to detect the structures in-line with railway track geometry such as railway crossings, turnouts and quantitatively estimate their dimensions and spatial location by iteratively applying a vertical slice to point cloud data for long distance laser measurement. The rectangular vertical slices were defined and their boundary coordinates were estimated based on a geometrical method. Estimated vertical slice boundaries were iteratively used to evaluate the point density of each vertical slice along with a cross-track direction of the railway line. Those point densities were further analyzed to detect the railway line track objects by their shape and spatial location along with the rail bed. Herein, the survey dataset is used as a dictionary to preidentify the spatial location of the object and then as an accurate estimation for the rail-track, by estimating the gauge corner (GC) from dense point cloud. The proposed method has shown a significant improvement in the rail-track extraction process, which becomes a challenge for existing remote sensing technologies. This adaptive object detection method can be used to identify the railway track structures prior to the railway track extraction, which allows in finding the GC position precisely. Further, it is based on the parallelism of the railway track, which is distinct from conventional railway track extraction methods. Therefore it does not require any inertial measurements along with the MLS survey and can be applied with less background information of the observed MLS point cloud. The proposed algorithm was tested for the MLS data set acquired during the pilot project collaborated with West Japan Railway Company. The results indicate 100% accuracy for railway structure detection and enhance the GC extraction for railway structure monitoring.

Information modelling of track geometry

The objective of this study is to substantiate a new method for modelling the railway track geometry. The method includes a new way of path measuring and the resulting method for modelling of track geometry. There can be two variants of track measuring with the new method. The first variant includes measuring only the lengths of line segments between the marked points. The second variant includes measuring lengths, angles and coordinates. The article describes the measuring technique and the modelling mechanism and compares the new method with the traditional one. The method is applicable for measuring and modelling any large spatial object such as a pipeline or a sea craft. The advantage of the new method is the efficiency of work and calculations. The modelling can be done on site using any portable computer.

Optimal opportunistic tamping scheduling for railway track geometry

This study has been dedicated to the optimization of opportunistic tamping scheduling. The aim of this study has been to schedule tamping activities in such a way that the total maintenance costs and the number of unplanned tamping activities are minimized. To achieve this, the track geometry tamping scheduling problem was defined and formulated as a mixed integer linear programming (MILP) model and a genetic algorithm was used to solve the problem. Both the standard deviation of the longitudinal level and the extreme values of isolated defects were used to characterize the track geometry quality and to plan maintenance activities. The performance of the proposed model was tested on data collected from the Main Western Line in Sweden. The results show that different scenarios for controlling and managing isolated defects will result in optimal scheduling plan. It is also found that to achieve more realistic results, the speed of the tamping machine and the unused life of the track sections should be considered in the model. Moreover, the results show that prediction of geometry condition without considering the destructive effect of tamping will lead to an underestimation of the maintenance needs by 2%.

Investigating Root Causes of Railway Track Geometry Deterioration – A Data Mining Approach

Railway track geometry deterioration indicates degradation in the underlying track structures. Monitoring and predicting this behavior are important, as is investigating the of root causes contributing to the deterioration. Without knowing the causes, assigned remediation might not result in a long-lasting correction. However, there is little research regarding the pragmatic aspects of investigating the root causes of track geometry deterioration utilizing real-world data sources. For this purpose, a new method was explored. After reviewing methodologies, the chosen approach was an association rule data mining method Generalized Unary Hypothesis Automata (GUHA). The initial data used in data mining comprises data from asset management and multiple measurement systems, including a track geometry measurement vehicle, a track stiffness measurement device, ground penetrating radar, and Lidar. The results of the GUHA data mining are hypotheses based on the initial data, which can be used to indicate the most common and uncommon types of structures regarding their track geometry deterioration behavior and the attributes governing the behavior of a certain structure type. Therefore, the GUHA method was found to be a suitable method for investigating the root causes of track geometry deterioration from comprehensive railway track structure data.

Fractal analysis of high speed rail geometry data: A case study of Ankara-Eskişehir high speed rail

Abstract By considering railway track geometry as a fractal pattern, the irregularity of the track geometry can be expressed numerically with the help of fractal dimensions. In this study, a novel algorithm based on ruler method has been developed and a program was written to determine the fractal dimensions of railway track geometry graphs. Four different fractal dimensions of DR1, DR2, DR3, and DR4 were proposed to determine the geometric irregularity of the railway track by using the data of Ankara-Eskisehir High-Speed Railway track. DR1 and DR2 were used to quantify short wavelength irregularities while DR3 and DR4 were used to quantify medium wavelength irregularities. At the end of the study, the relationship between fractal dimensions and standard deviation values, which is the quality indicator according to EN 13848-6, was investigated. According to this, there is a strong relationship between the DR3 and the standard deviation.

Preliminary study of shaping the railway track geometry in terms of their maintenance costs and capacity

In Poland, due to the increase in investments made by railways in recent years, and thus the increase in the replacement value of transport infrastructure, the need for expenditure on infrastructure maintenance will increase in the next 30 years, or the development of the developed transport network will degrade. As part of the overall discipline of resource management, subdiscipline has emerged - infrastructure asset management. As part of the management of railway transport infrastructure, the demand for cheaper maintenance costs will grow. The cost reduction of infrastructure maintenance is possible through meticulous assessment of its condition, rational selection of locations and scope of repairs at the assumed risk level, as well as at the stage of preparation of new construction or modernization projects taking into account aspects of later maintenance. For some time, we have been observing the accumulation of knowledge (methods, programs, procedures) in the country and abroad enabling optimization of infrastructure condition assessment and programming of its maintenance. The implementation of these solutions may result in a more rational use of funds for infrastructure maintenance and not disturb its smooth functioning in operation. The article discusses aspects that should be considered in the design process of railway infrastructure. Particular attention was paid to the durability of steel components of the railway superstructure, maintenance costs as well as aspects related to the capacity of the track node. An example of dependence of selected values of radial arcs depending on their durability and maintenance costs was presented. It was proposed to change the track layout at the Warszawa Srodmiescie passenger stop planned for reconstruction. Calculations of kinematic parameters for various configurations of railway turnouts were performed. Also, calculations of the capacity for the existing track system solution as well as the proposed track system after reconstruction of the analysed Warszawa Srodmiescie railway station were also carried out.

Effective time interval for railway track geometry inspection

A proper decision-making scheme for track geometry maintenance requires a knowledge of the real condition of track geometry. Therefore, the track must be inspected by measurement cars at different time intervals. The frequency of track geometry inspection plays a crucial role in decision-making and has always been a big concern for infrastructure managers. The inspection interval should be chosen properly, it means that the small period can decrease the capacity of line and affect the operation of network and the big period can result in low quality of track and in some cases derailments and possible loss of human lives. The aim of this paper is to determine the effective inspection interval such that the total maintenance cost is minimized. In the proposed cost model, the costs of inspection, preventive maintenance, corrective maintenance and the penalty for exceeding the corrective maintenance level are considered. A case study is performed on a real dataset collected from a railway line in Iran. The standard deviation of longitudinal level is considered to measure track geometry degradation. A widely applied linear model is used to model track geometry degradation over time. Monte Carlo technique is used to simulate the track geometry behavior under various track geometry inspection intervals. In addition, a set of sensitivity analyses are carried out to assess the effect of various inspection intervals on different terms of maintenance cost. The results indicate that not only can substantial costs be saved by setting effective inspection intervals, but also the time during which the track suffers from bad conditions is dramatically reduced. The result of this study has shown the appropriate inspection interval for the studied case can result in 13.6 percent decrease in maintenance cost in comparison with the current maintenance policy. Besides, it would lead to more reliable railway track by preventing the system exceed the corrective threshold.