Relay-based traffic control systems are still used in railway control systems. Their correctness is most often verified by manual analysis, which does not guarantee correctness in all conditions. ...Passenger safety, control reliability, and failure-free operation of all components require formal proof of the control system’s correctness. Formal evidence allows certification of control systems, ensuring that safety will be maintained in correct conditions and the in event of failure. The operational safety of systems in the event of component failure cannot be manually checked practically in the event of various types of damage to one component, pairs of components, etc. In the article, we describe the methodology of automated system verification using the IMDS (integrated model of distributed systems) temporal formalism and the Dedan tool. The novelty of the presented verification methodology lays in graphical design of the circuit elements, automated verification liberating the designer from using temporal logic, checking partial properties related to fragments of the circuit, and fair verification preventing the discovering of false deadlocks. The article presents the verification of an exemplary relay traffic control system in the correct case, in the case of damage to elements, and the case of an incorrect sequence of signals from the environment. The verification results are shown in the form of sequence diagrams leading to the correct/incorrect final state.
Temeljni cilj ovoga rada jest istražiti i analizirati uzroke nastanka izvanrednih događaja u željezničkom prometu. Svrha rada jest prepoznati glavne uzročnike nastanka izvanrednih događaja kako bi ...moguće korektivne akcije rezultirale maksimalnim povećanjem sigurnosti željezničkog prometa. Rezultati istraživanja temelje se na sekundarnim podacima o uzrocima nastanka izvanrednih događaja na prugama HŽ Infrastrukture za razdoblje od 2014. do 2019. godine. U radu su korištene znanstvene metode analize i sinteze, metode deskriptivne statistike te Pareto grafikon. Glavni nalaz ovoga rada upućuje na zaključak da su nesmotreno ili zlonamjerno djelovanje drugih osoba i tehnički nedostatak na infrastrukturnim podsustavima ili vozilima upravitelja infrastrukture odgovorni za 83,7 % izvanrednih događaja na prugama HŽ Infrastrukture, dakle više od svih drugih uzročnika zajedno.
The main goal of this work is to investigate and analyze the causes of extraordinary events in railway traffic. The purpose of the work is to identify the main causes of the occurrence of extraordinary events so that possible corrective actions result in a maximum increase in the safety of railway traffic. The results of the research are based on secondary data on the causes of extraordinary events on the tracks of Croatian Railway Infrastructure for the period from 2014 to 2019. Scientific methods of analysis and synthesis, methods of descriptive statistics and the Pareto chart were used in the work. The main finding of this paper points to the conclusion that reckless or malicious actions of other persons and technical defects in infrastructure subsystems or vehicles of the infrastructure manager are responsible for 83.7% of extraordinary events on the tracks of Croatian Railway Infrastructure, i.e. more than all other causes combined.
The present paper focuses on the experimental validation of a numerical approach previously proposed by the authors for the prediction of vibrations inside buildings due to railway traffic in ...tunnels. The numerical model is based on the concept of dynamic substructuring and is composed by three autonomous models to simulate the following main parts of the problem: i) generation of vibrations (train–track interaction); ii) propagation of vibrations (track–tunnel–ground system); iii) reception of vibrations (building coupled to the ground). The experimental validation consists in the comparison between the results predicted by the proposed numerical model and the measurements performed inside a building due to the railway traffic in a shallow tunnel located in Madrid. Apart from the brief description of the numerical model and of the case study, the main options and simplifications adopted on the numerical modeling strategy are discussed. The balance adopted between accuracy and simplicity of the numerical approach proved to be a path to follow in order to transfer knowledge to engineering practice. Finally, the comparison between numerical and experimental results allowed finding a good agreement between both, fact that ensures the ability of the proposed modeling strategy to deal with real engineering practical problems.
•A numerical approach for prediction of vibrations due to subway traffic is proposed;•The experimental validation of the numerical approach is performed;•The proposed numerical approach is useful for the study of mitigation solutions.
Railway shunting accidents, in which trains collide with obstacles, often occur because of human error or fatigue. It is therefore necessary to detect traffic objects in front of the trains and ...inform the driver to take timely action. To detect these objects in railways, we proposed an object-detection method using a differential feature fusion convolutional neural network (DFF-Net). DFF-Net includes two modules: the prior object-detection module and the object-detection module. The prior module produces initial anchor boxes for the subsequent detection module. Taking the initial anchor boxes as input, the object-detection module applies a differential feature fusion sub-module to enrich the sematic information for object detection, enhancing the detection performance, particularly for small objects. In experiments conducted on a railway traffic dataset, compared with the current state-of-the-art detectors, the proposed method exhibited significant higher performance and was more effective and more efficient than the other methods for object detection in railway tracks. Additionally, evaluation results based on PASCAL VOC2007 and VOC2012 indicated that the proposed method was significantly better than the state-of-the-art methods.
•We survey the emerging technology of ATO in railway systems in theoretical and practical aspects.•The motivation, development and structure of existing ATO systems are explicitly introduced.•The ...classification and a comprehensive literature review are presented.•The emerging requirements for current ATO systems and the future research directions are discussed.
With the rapid development of communication, control and computer technologies in the last several decades, automatic train operation (ATO), for which the driver no longer has to cautiously operate the control handle, is emerging in many urban rail systems to replace traditional manual driving in recent years. As technology advances in railway systems, one theoretically challenging and practically significant problem is how to use the ATO system to make the current railway network more efficient with higher carrying capacity, lower cost and improved quality of service by optimized railway traffic management and train operation. In this review, we focus on this emerging technology of automatic train operation (ATO) for its theoretical development and practical implementations. Specifically, this study first presents the background of ATO technology in railways, which involves the detailed description of its development and implementation in urban metro systems, fundamental features and basic structure of a typical ATO system. Then, we present a comprehensive literature review in this area, in which the current studies are generally classified into three main aspects, i.e., train operation modeling techniques, train trajectory optimization and train speed control methods. Finally, the emerging requirements for current ATO systems and the most promising research directions in this area in the future are discussed explicitly, including (i) the practical implementation of ATO in main line and high-speed railways, (ii) the cooperative train operation methods for energy-saving issues and (iii) the integration of railway traffic control with advanced ATO technology.
•We model the delay of a train over time as a stochastic process.•We combine domain dependent knowledge and machine learning approaches.•Based on collected data, we train a Bayesian inference ...network.•The approach shows very small errors for prediction up to 30 min.•The dynamics of the delay prediction within the time horizon is studied in detail.
In this paper we present a stochastic model for predicting the propagation of train delays based on Bayesian networks. This method can efficiently represent and compute the complex stochastic inference between random variables. Moreover, it allows updating the probability distributions and reducing the uncertainty of future train delays in real time under the assumption that more information continuously becomes available from the monitoring system. The dynamics of a train delay over time and space is presented as a stochastic process that describes the evolution of the time-dependent random variable. This approach is further extended by modelling the interdependence between trains that share the same infrastructure or have a scheduled passenger transfer. The model is applied on a set of historical traffic realisation data from the part of a busy corridor in Sweden. We present the results and analyse the accuracy of predictions as well as the evolution of probability distributions of event delays over time. The presented method is important for making better predictions for train traffic, that are not only based on static, offline collected data, but are able to positively include the dynamic characteristics of the continuously changing delays.
This paper addresses the problem of train conflict detection and resolution, which is dealt every day by traffic controllers to adapt the timetable to delays and other unpredictable events occurring ...in real-time. We describe a number of algorithmic improvements implemented in the real-time traffic management system ROMA (Railway traffic Optimization by Means of Alternative graphs), achieved by incorporating effective rescheduling algorithms and local rerouting strategies in a tabu search scheme. We alternate a fast heuristic and a truncated branch and bound algorithm for computing train schedules within a short computation time, and investigate the effectiveness of using different neighborhood structures for train rerouting. The computational experiments are based on practical size instances from a dispatching area of the Dutch railway network and include complex disturbances with multiple late trains and blocked tracks. Several small instances are solved to optimality in order to compare the heuristic solutions with the optimum. For small instances, the new tabu search algorithms find optimal solutions. For large instances, the solutions generated by the new algorithms after 20
s of computation are up to more than 15% better than those achieved within 180
s by the previous version of ROMA.
Railway timetables are developed to make operations robust and resilient to small delays. However, disturbances perturb the daily plan, and dispatchers adjust the plan to keep operations feasible and ...to limit delay propagation. Rescheduling approaches aim at updating the offline timetable at best, in the presence of delays. We present a survey of the recent approaches on online railway traffic rescheduling problems, which exhibit dynamic and stochastic (or, at least, not completely deterministic) aspects. In fact, while online static rescheduling has reached a wide degree of dissemination, much is still to be done with regard to the probabilistic nature of the railway traffic rescheduling problems, and also how to best take uncertainty into account for future states. Open challenges for the future research are finally outlined.
The article presents a model of connection of ETCS application and classical base layer equipment. The model distinguishes three layers: physical, logic and data, which require different modelling ...techniques and at the same time must be consistent. The model will form the basis for the digital mapping in the Digital Twin of the ETCS application. Layer division is a natural way to represent the structure of a device and its operating rules. It allows a detailed and structured representation of the interfaces of a connection and then an analysis of the connection both with respect to the layer of interest and from the point of view of the interaction between features in the different layers. The S-interface of the LEU encoder of the ETCS is described, taking into account different solutions encountered in practice. The conditions of the connection between the LEU encoder and the environment form a description of one of the two boundaries between the ETCS application, i.e. the implemented ERTMS/ETCS on a specific area of the railway network, and the environment. A general connection model and definitions of a connection and an interface are presented. As an example, the electrical connection with signals transmitted through galvanic connections has been assumed to be typical for LEU encoder and track-side signalling control circuits found in base layer equipment. The physical layer is described in terms of physical parameters and their values. The parameters are divided into electrical (current, voltage and frequency) and mechanical ones (number of leads, conductor thickness, etc.). The values of the electrical parameters are expressed in terms of a uncountable set with defined limits. The logic layer was described in a vector-matrix form. Logic signals are assigned to electrical signals with specific physical parameters. The data layer contains information about the assignment of specific telegrams to specific electrical signals.
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