AGUSTIN DE BETANCOURT AS CREATOR OF OPTICAL TELEGRAPH MACHINE USED ON THE FIRST EUROPEAN RAILWAY LINES AND PRECURSOR OF RAILWAY SIGNALLING SYSTEMS

The origin of signalling principles, their purpose and development since the 4th century BC are described. Claude Chappe' s research on the peculiarities of human vision and the rationale for the choice of colors for the optical telegraph are presented. These principles are used in modern rail and road signaling systems with slight modifi cations to refl ect the development of technology. The transmission apparatus and the Claude Chappe alphabet are presented, documentary examples of its use in France are proposed, and the main disadvantages of this principle of data transmission are indicated. Further in the article, an alternative principle of data transmission using a single semaphore wing in an optical telegraph is presented. It was developed and introduced in 1798 between Madrid and Cadiz (Spain) by Agustin de Betancourt. The article shows the diagrams of the optical telegraph apparatus of Agustin de Betancourt, and also gives its comparison with fi rst mechanical signals used in railway transport. With references to historical documents and evidence, the evolution of the optical telegraph by Agustin de Betancourt from data transmission systems between cities to systems for the exchange of information between neighboring railway posts and stations on the fi rst railway lines is presented. The evolution of the telegraph from mechanical devices announcing the train approach to the railway post to the signals for train drivers thanks to the change of wing position is shown. As a transitional stage from mechanical to electrical signals in railway transport, the principle of operation of semaphores with kerosene lamps lit at night with light fi lters mechanically connected to the position of the wing is explained. Based on development of mechanical signals, the historical reasons for signal aspect with two lamps in diff erent modern signalling systems are presented. The article opens a new, previously little-known page of the activities by Agustin de Betancourt, who was not only the fi rst rector of the fi rst transport high school in Russia but also one of developers of data transmission systems used optical telegraph. His inventions such as mechanical signal with one wing are using in improved form in railway signalling systems up today.

A refinement-based development of a distributed signalling system

The decentralised railway signalling systems have a potential to increase capacity, availability and reduce maintenance costs of railway networks. However, given the safety-critical nature of railway signalling and the complexity of novel distributed signalling solutions, their safety should be guaranteed by using thorough system validation methods. To achieve such a high-level of safety assurance of these complex signalling systems, scenario-based testing methods are far from being sufficient despite that they are still widely used in the industry. Formal verification is an alternative approach which provides a rigorous approach to verifying complex systems and has been successfully used in the railway domain. Despite the successes, little work has been done in applying formal methods for distributed railway systems. In our research we are working towards a multifaceted formal development methodology of complex railway signalling systems. The methodology is based on the Event-B modelling language which provides an expressive modelling language, a stepwise development and a proof-based model verification. In this paper, we present the application of the methodology for the development and verification of a distributed protocol for reservation of railway sections. The main challenge of this work is developing a distributed protocol which ensures safety and liveness of the distributed railway system when message delays are allowed in the model.

Reliability and Inspection Modelling of Railway Signalling Systems

The railway is one of the most prominent models of transportation across the globe and it carries a large number of people, thus requiring high reliability, maintainability and safety. The reliability of railways mostly depends on an effective signalling system, making it one of the critical parts of railway operation. A signalling system is part of a large array of systems with interconnected components and subcomponents. Therefore, there is a need to make the signalling system more reliable and optimised with enhanced fault detection. Proper inspection and maintenance are required to make the signalling system reliable and safe. In this study, different inspection modelling techniques are applied to find the reliability of the signalling system. The signalling system has been divided into subsystems (signal unit, track unit, point-and-point machine) considering their importance and their effects on the failure rate of the entire signalling system. Inspection modelling of each subsystem has been conducted to provide the basis for the entire signalling system. A case study has been investigated to validate the model developed in one of the busiest tracks in eastern India. The obtained data thus are used to analyse the inspection pattern of signalling subsystems. Special attention to maintenance for inspection activities and logistics support has been taken into consideration, which is required to improve the reliability and maintainability of signalling subsystems and systems to make the railway signalling system sustainable in the long run.