Simulating Train Dispatching Logic with High-Level Petri Nets

Railway simulation is commonly used as a tool for planning and analysis of railway traffic in operational, tactical and strategical level. During the simulation, a typical problem is a deadlock, i.e. a specific composition of trains on a simulated section positioned in such a way that they are blocking each other\u27s paths. Deadlock avoidance is very important in the simulation of railways because deadlock can stop the simulation, and significantly affect the simulation results. Simulation of train movements on a single track line requires implantation of additional rules and principles of train spacing and movement as train paths are more often in conflict than on a double track line. A High-level Petri Nets simulation model that detects and manages train path conflicts on a single track railway line is presented. Module for train management is connected to other modules on a hierarchical High-level Petri net. The model was tested on a busy single track mainline between Hrpelje-Kozina and Koper in south-western Slovenia

Complete Model-Based Testing Applied to the Railway Domain

Testing is the most important verification technique to assert the correctness of an embedded system. Model-based testing (MBT) is a popular approach that generates test cases from models automatically. For the verification of safety-critical systems, complete MBT strategies are most promising. Complete testing strategies can guarantee that all errors of a certain kind are revealed by the generated test suite, given that the system-under-test fulfils several hypotheses. This work presents a complete testing strategy which is based on equivalence class abstraction. Using this approach, reactive systems, with a potentially infinite input domain but finitely many internal states, can be abstracted to finite-state machines. This allows for the generation of finite test suites providing completeness. However, for a system-under-test, it is hard to prove the validity of the hypotheses which justify the completeness of the applied testing strategy. Therefore, we experimentally evaluate the fault-detection capabilities of our equivalence class testing strategy in this work. We use a novel mutation-analysis strategy which introduces artificial errors to a SystemC model to mimic typical HW/SW integration errors. We provide experimental results that show the adequacy of our approach considering case studies from the railway domain (i.e., a speed-monitoring function and an interlocking-system controller) and from the automotive domain (i.e., an airbag controller). Furthermore, we present extensions to the equivalence class testing strategy. We show that a combination with randomisation and boundary-value selection is able to significantly increase the probability to detect HW/SW integration errors

Optimal Train Rescheduling in Oslo Central Station

Real-time train dispatching (i.e., rescheduling and replatforming) in passenger railway stations is a very important and very challenging task. In most major stations, this task is carried out by hand by highly trained dispatchers who use their extensive experience to find near-optimal solutions under most conditions. With several simultaneous deviations from the timetable, however, the traffic situation may become too complex for any human to handle it far beyond finding feasible solutions. As part of a prototype for a dispatching support tool developed in collaboration with Bane NOR (Norwegian rail manager), we develop an approach for Optimal Train Rescheduling in large passenger stations. To allow for replatforming, we extend the standard job-shop scheduling approach to train-scheduling, and we develop and compare different MILP formulations for this extended approach. With this approach, we can find, in just a few seconds, optimal plans for our realistic instances from Oslo Central Station, the largest passenger train hub in Norway. The prototype will be tested by dispatchers in the greater Oslo area, starting from the fall of 2021.publishedVersio

Railway freight node capacity evaluation: A timetable-saturation approach and its application to the Novara freight terminal

Abstract This paper presents a timetable-based approach to assess the capacity of a railway freight node, based on the microscopic simulation and saturation of the timetable. Saturation is done by scheduling additional saturation train paths without introducing any traffic conflict, while respecting the required technical and operational constraints, until no more paths can be added. The approach is applied to analyze the potential effects on capacity of some infrastructure improvements planned by Rete Ferroviaria Italiana (RFI) for the rail freight node of Novara, Italy. The capacity is evaluated by means of two KPIs computed on saturated timetables: the number of daily pairs of saturation freight trains and the infrastructure Occupancy Time Rate (OTR). The first KPI represents an absolute estimation of the capacity (theoretical or practical, depending on the presence of buffer times). Instead, the OTR is computed by the UIC 406R compression method and it is used to identify local bottlenecks. For the analysis, we use SASTRE, an analysis environment for railway systems developed at Politecnico di Torino, which combines a MILP formulation for the timetable saturation problem with a saturation strategy layer. The saturation strategy considers a given set of priorities between the different network areas and the train types to be used during the saturation process. The results reveal that using a microscopic model to schedule traffic flows on a complex railway node allows for a good accuracy of the timetable, but at a high computational cost

Railway Signalling Principles

This tutorial E-book is based on the long-standing experience of teaching railway operations and signalling at TU Braunschweig and other universities and higher vocational training institutions in different parts of the world. It explains the fundamental principles all railway signalling systems have in common. This is done in a generic way that does not focus on specific national solutions. It covers basic elements and terms, principles for safe train separation, interlocking principles, automatic train protection, and level crossing protection. It also contains a glossary with definitions of relevant terms

Train driver automation strategies to mitigate signals passed at danger on South African railways

A research project report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Masters in Engineering. Date 2018/04/18Train derailments or collisions have the potential to result in catastrophic loss of life and/or destruction of property. Ever higher demands for train density (i.e. trains per hour for a given section of track) as well as the catastrophic results when accidents do occur have given rise to the development of railway signalling systems as mitigation measures (Rolt, 2009; Theeg & Vlasenko (2009b). Signals Passed At Danger (SPADs) refers to when a train driver passes a stop signal without authority and is one of the typical causes of such accidents resulting in significant damages reported within Transnet Freight Rail (TFR) in recent years. Studies have shown human train driver error and violation of signals to be a significant cause of SPAD events. This study investigated the application of train driver automation as a mitigation measure against SPADs within the South African railway environment in general and TFR in particular. The study was qualitative in nature, following a model development methodology and used in-depth, semi-structured interviews with railway signalling engineers for data collection. The primary goal was defined to be the development of a train driver function automation method that could be considered the most appropriate within the TFR operational environment. The study determined the most appropriate method to be that of having a human driver with technical supervision. In this arrangement, the human driver could remain in his conventional role of driving the train but with a technical supervision system superimposed that automatically intervenes if a train driver exceeds his movement authority (e.g. Automatic Train Protection or ATP). This approach mitigates many of the costs imposed by human failure associated with SPAD events, yet retains the value of human flexibility which is especially useful under abnormal circumstances.MT 201

A Set Packing Inspired Method for Real-Time Junction Train Routing

Efficiently coordinating the often large number of interdependent, timetabled train movements on a railway junction, while satisfying a number of operational requirements, is one of the most important problems faced by a railway company. The most critical variant of the problem arises on a daily basis at major railway junctions where disruptions to rail traffi c make the planned schedule/routing infeasible and rolling stock planners are forced to reschedule/re-route trains in order to recover feasibility. The dynamic nature of the problem means that good solutions must be obtained quickly. In this paper we describe a set packing inspired formulation of this problem and develop a branch-and-price based solution approach. A real life test instance arising in Germany and supplied by the major German railway company, Deutsche Bahn, indicates the efficiency of the proposed approach by confirming that practical problems can be solved to within a few percent of optimality in reasonable time

Analysis of Railway Signalling Systems to Increase Line and Node Capacity

"Europe is one of the most urbanized continents on the planet: about 75% of its population lives in urban areas” (European Enviroment Agency, 2017). In this urban context, the car is still the widely used way of transport, while public transport manages to capture residual segments of the demand for mobility. However, in a structural framework of obvious concern and criticality for public transport, there is a component of the sector in strong expansion, that is, all rail transports. In addition, the incidence of rail transport is even more significant in large metropolitan systems where daily travel reaches its highest levels of expression. It is known, however, that the supply of transport services is limited by the capacity of the transport system which depends on the physical size of the infrastructure, that is, the capacity of the infrastructure, the number of vehicles, the capacity of the vehicle fleet, the operating time and the traffic regime implemented