Railway Signalling

The development of computer controlled Railway Interlocking Systems (RIS) has seen an increasing interest in the use of Formal Methods, due to their ability to precisely specify the logical rules that guarantee the safe establishment of routes for trains through a railway yard. Recently, a trend has emerged about the use of statecharts as a standard formalism to produce precise specifications of RIS. This paper describes an experience in modelling a railway interlocking system using statecharts. Our study has addressed the problem from a “geographical”, distributed, point of view: that is, our model is composed by models of single physical entities (points, signals, etc..) that collectively implement the interlocking rules, without any centralized database of rules, which is on the other hand a typical way of implementing such a system (what we call “functional ” approach). One of the main aims of our approach, is to verify its ability to reduce revalidation efforts in the case of p...

The dynamic analysis of the safety critical software is an important phase of the Independent Verification and Validation of the system. The EN 50128 has detailed the methods that shall be used for this phase of the verification life cycle. This phase is so critical to the project output that it demands meticulous planning and organization. Here we discuss the dynamic analysis methods suggested by the CENELEC standards for SIL 4 software

Railway Signalling is safety critical domain, where still traditional technology is in use. There are many reasons for using traditional technology; one of the main reasons being the proven Safety performance of the older systems (Relay Based). As the rail traffic is increasing and with higher speed of trains there is an acute need for modernization of Railway Signalling Technology. Even with the advent of Microprocessor based technology, the problems have not been solved. This article
proposes the use of Wireless sensor networks in Railway Signaling domain which combines the Ground base signalling and the On–Board Signalling, which is suitable for high Speed Railway Traffic. The article gives brief idea of the architectures of a Sensor Node, Driver node, Gateway Node and Base Station. It discusses the network Architectures and the Routing algorithms to be used in the sensor networks. It also discusses the design of Control laws (Interlocking Logic) for safe movement of trains
and also the failsafe techniques to be used in the design of such Technology. The article also describes the challenges in using the Concept of Wireless Sensor Networks in Railway Signalling Domain.

A railway signalling system is safety critical system that controls the traffic which includes train routes, shunting moves and the movements of all other railway vehicles in accordance with railway rules, regulations and technological processes required for the operation of the railway system. The overall signalling system consists of Microprocessor based Wayside controllers, On-board systems controlling the railway vehicle and
supervision systems to monitor the vehicle movements from a centralized location. The complex nature of
railway signalling rules and operational practices adopted by different railroads pose a difficult task for the
software development of these systems. The complex nature of the software poses an even more challenging
task during the Independent Verification and Validation of the system. The CENELEC set of standards is the
widely accepted as the governing standard for design, development and Independent Verification and
Validation (IV&V) of railway signalling systems. This paper describes the challenges faced during the
different phases of IV&V of safety critical railway signalling software which is unique compared to other
domains.

The railway signalling domain is a safety critical domain, where safety is given utmost importance. The railway signalling domain is mostly operated using traditional technology, which is considered safe and time proven. The New advances in technology have not been able to solve age old problems of safety and reliability. Here we give brief of the signalling domain and signalling concepts

Perhitungan kapasitas stasiun memiliki peran penting dalam upaya peningkatan kapasitas pengoperasian kereta api dan pengembangan prasarana perkeretaapian, serta melakukan pengawasan dan pembinaan kepada penyelenggara prasarana perkeretaapian. Kompleksitas faktor yang mempengaruhi metode perhitungan kapasitas stasiun tidak dapat dilepaskan dari perhitungan Conflict Rate untuk memperoleh nilai dari kapasitas sistem interlocking Kapasitas sistem interlocking dapat diinvestigasi dengan metode simulasi sederhana menggunakan Tabel Konflik Pembentukan Rute KA di Stasiun. Dengan bantuan tabel konflik rute tersebut, persentase terjadinya konflik (Conflict Rate) dapat ditentukan sebagai perbandingan antara jumlah dari kombinasi rute berkonflik dengan jumlah total dari kombinasi rute yang dapat terbentuk. Semakin besar Conflict Rate, maka semakin kecil kapasitas sistem interlocking, sehingga menyebabkan kapasitas stasiun akan semakin kecil pula. Perhitungan kapasitas sistem interlocking perlu dikaji lebih mendalam dengan mempertimbangkan jumlah kereta api berdasarkan rute yang terbentuk untuk mendapatkan hasil yang lebih akurat dan untuk melihat kemudahan aplikasinya di lapangan sesuai dengan karakteristik masing-masing stasiun yang ada di Indonesia. Perhitungan kapasitas sistem interlocking kedepannya dapat digunakan sebagai salah satu variabel penting dalam menyusun formulasi perhitungan kapasitas stasiun yang harus memenuhi syarat flexibilitas berbagai kondisi dan karakteristik stasiun di dalam sistem perkeretaapian Indonesia tanpa meninggalkan prinsip-prinsip keselamatan operasi.

The paper presents the practical results of some of the projects done by the Russian Railways company with the direct involvement of JSC NIIAS researchers and developers. The focus is made on the vision and challenges of ongoing digitisation of command and control in view of transition to new paradigms of train separation, train detection and localization.

In this study, a centralized automatic block controller that ensures fail-safe interlocking in open line and between the exit routes facing each other of two neighbouring stations are developed for fixed block signalling systems. In this way, a protected track form is created that ensures protection against following and opposing movements across the open line. State transition diagrams are used as the modelling method, since fixed block signalling systems have similar characteristics as mutually discrete event systems (DES), and since this method is recommended in the IEC 61508-3 and EN 50128 standards. Diversely, existing studies in the literature, the logical equalities obtained in the state transition diagrams are converted to PASCAL language-based, high level SCL language PLC code, which is also quite recommended for SIL 4 in the aforementioned standards. In conclusion, the block controller is verified with the TIA Portal and PLCSIM.

The development of computer controlled Railway Interlocking Systems (RIS) has seen an increasing interest in the use of Formal Methods, due to their ability to precisely specify the logical rules that guarantee the safe establishment of routes for trains through a railway yard. Recently, a trend has emerged about the use of statecharts as a standard formalism to produce precise specifications of RIS. This paper describes an experience in modelling a railway interlocking system using statecharts. Our study has addressed the problem from a “geographical”, distributed, point of view: that is, our model is composed by models of single physical entities (points, signals, etc..) that collectively implement the interlocking rules, without any centralized database of rules, which is on the other hand a typical way of implementing such a system (what we call “functional ” approach). One of the main aims of our approach, is to verify its ability to reduce revalidation efforts in the case of p...

The main issue in controlling safety-critical systems such as nuclear power reactors or railway interlocking systems is to provide high safety and reliability where the risk ratio is at the highest level because small errors might result in hazardous accidents (e.g., death or injury of many people). The N-version programming technique, where N-different modules run in parallel, can be used to improve the reliability and safety of such systems at the desired safety level. Decisions of N-different modules are then evaluated by another component, usually known as the voter, using different voting strategies. In the current study a bitwise voting strategy to evaluate module decisions that are based on safe-states of variables is proposed and possible synchronization problems between the modules are determined. Sequence diagrams and solutions for synchronization problems are also explained.