Safety Of Railway Systems Research Articles

Analytical Study on the Safety of High Speed Railway Vehicle on Excited Tracks

A railway is organized by a variety of individual technologies, and functions safely and properly as a system, therefore it is necessary for the system safety to study each potential case of disasters caused by earthquakes. Recent reports imply that railway vehicles could derail solely by the ground motions of earthquakes without fatal damages of vehicles or tracks. Based on the reports and facts, we believe that we should further study the derailment mechanism of a high speed railway vehicle excited by great seismic motions, to pursue to minimize the risk of railway system safety against great earthquakes. At the start of the study, we developed our original vehicle dynamics simulation and then employed it for numerical analyses. At the present stage, through the analyses, we obtained the following major outcomes. (1) Most of derailments are brought as the result of the rocking motion of a vehicle by track excitations underneath. Interestingly, the derailing motions are observed similarly regardless of vehicle speed. (2) By contrast, the excitation amplitudes for derailment are influenced by vehicle speed particularly in lower input frequencies. This can be explained by the sensitivity of the relative wheel/rail slide due to creepage. (3) The excitation amplitudes for 30 mm of wheel lift are relatively independent of vehicle speed. (4) The wheel/rail slide strongly depends on the friction coefficient if a vehicle stationed, being relatively independent of the friction coefficient at higher speeds.

Reliability and Safety of Railway Systems(Dependability of Social Systems)

Reliability and Safety of Railway Systems(Dependability of Social Systems)

Safety of Application Programming for Railway Signal Controllers

A model that provides a framework for assessing verification and validation techniques for application programming for the safety of railway signaling systems is presented. A railway signaling system is a logical controller, also known as interlocking, that ensures that conflicting train movements are not signaled. The signal interlockings, as a data-driven systems sets out a logical relationship and instructions which comprise the procedures by which the interlocking implements the required signaling functions. The safety assurance is assessed by Intensity Capability of the inspection system, effect of application parameters, and the effect of human and environmental factors. The code inspection analyzes program behavior by producing programs from interpretation of codes and checks the applicability of codes in the event of fatigue or loss of concentration, to evaluate errors in complex railway processes.

Geodetic survey and track recording vehicle data combined for the accurate setting out of rails on slab track

Track geometry quality is a critical factor for the safety of modern railway systems. It is achieved through a number of track surveying parameters that, in essence, characterize the quality of the absolute and relative rail locations. Nowadays, two methods are widely used for acquiring accurate track surveying data; standalone geodetic surveys and kinematic track measuring systems. Despite the rapid growth in the use of track recording trolleys in the past few years, it has become clear that, depending on the special features of a construction project, the combineduse of both systems can increase the reliability of track geometry quality with profound effects on construction costs and operational safety. This paper presents the basic concept of track geometry surveying, describes the surveying techniques and compares the rail laying quality measures obtained from the implementation of the two methods during the construction of the modern tramway of Athens.

ATP/ATC subsystem testing and validation using a HIL test rig

Automatic Train Protection (ATP) systems ensure that trains comply with speed restrictions and prevents them passing red signals. They are designed in order to automatically act to slow or stop the train where trains exceed speed limits or pass signals at danger. Their safety and reliability is then crucial for the safety and efficiency of the whole railway system. A correct estimation of distance to target and actual velocity is fundamental to evaluate residual braking resources, in terms of available deceleration, in order to reach the targets at the required speeds. The so-called odometry algorithm is the ATP subsystem devoted to train speed and travelled distance evaluation: it is composed by a series of sensors and a software procedure that acquires and manages the information from the sensors. Odometry estimation accuracy has a great influence on the whole ATP system behavior and then has to be carefully designed and verified. The validation of such devices could be performed with test runs, but this procedure has some disadvantages, for example, it is expensive and presents management difficulties (since these test activities have to be integrated with the normal rail traffic), testing conditions are not completely controllable etc. In order to overcome all these problems, Trenitalia S.p.A. and the Energetics Department of Florence University has designed and realized a HIL (Hardware In the Loop) test rig for the type approval of odometry devices. In this work the main features of the odometry device developed for the Italian ATP system (named SCMT) will be shown, the criteria used to design the tests will be resumed, then the architecture of the test rig will be presented. The final part of the work will summarize the results obtained from the testing activities and an estimation of the odometry subsystem performance (in terms of speed and travelled distance accuracy).

On the fatigue design method for high-speed railway axles

Fatigue failure of the railway axle, which has been a source of difficulty for engineers since railroad service started in the early part of the nineteenth century, was the beginning of the study of metal fatigue. In order to maintain the safety of a high-speed railway system, a large number of investigations and experiments have been carried out by outstanding researchers ever since, and many improvements have been made in the material, manufacturing, heat treatment and design methods. In comparing Japan and Europe on the fatigue design philosophy of the high-speed railway axle, it is recognized that there is a difference between the Japanese Shinkansen and the European TGV and ICE. The critical parts for fatigue strength are the press-fitted parts which suffer from fretting fatigue damage, such as the wheel seat, gear seat and brake disc seat. In Europe, the larger diameter of the press-fitted part makes the fillet the critical part. In Japan, however, the fatigue strength of the press-fitted part is increased by an induction hardening method. Also, a stress-relief groove is made at the closely press-fitted part of the axle. For several years, no fretting fatigue cracks in Shinkansen axles have been detected by magnetic particle inspection. It is noted that improvements over many years have been successful in achieving the safety of high-speed railway axles. These problems will be studied in this paper.

Chapter 5: The Vital Processor Interlocking

This document is one of the parts of the electronic version of the PhD thesis by S.F.M. van Vlijmen [53]. The goal of the PhD project was to get a better understanding of the problems with the integration of formal specification technique in the day to day software practice. The approach followed was to execute a number of projects in cooperation with industry on realistic cases.This document reports on the modelling of a railway safety and control system in μCRL, the specification of set of practically relevant safety criteria in the modal logic for μCRL. Next, the means for verification of the criteria on the model are discussed. Reported is on tests of the verification of a small number of critera on a model of an actual safety system. Finally, the case study is evaluated.

Chapter 7: Epitomes of Four other Cases

This document is one of the parts of the electronic version of the PhD thesis by S.F.M. van Vlijmen [42]. The goal of the PhD project was to get a better understanding of the problems with the integration of formal specification technique in the day to day software practice. The approach followed was to execute a number of projects in cooperation with industry on realistic cases.In this document is reported on four other cases in a succint manner. For each case the system studied is described, the formal specification work done is discussed, and the case is evaluated.The first case describes the modelling in PSF of a model of a production facility for printed circuit boards. The second case is about the modelling of telephone services following the Service Independent Building block architecture. The language used was again PSF. The third case is about the syntax of a language for the programming of railway safety systems. Here the language definition system ASF+SDF was used. The fourth and final case is about a system that optimizes the replacement schedules for light bulbs in traffic regulation systems. ACP, PSF and Pascal are the languages used.