AŽD Praha (Czechia)

The structure of many current systems is independent of related responsibility borders. It comes from the fact that they are designed by programmers that as a rule give more importance to efficient data moving than to reflecting existing business and control processes and to precise personal or organizational responsibility. It results in non-trivial issues when looking for reasons and responsibility for improper system behaviour and its overall quality. Another serious issue is that the requirements on the systems are changing during their development and use. Accommodation to the changes often introduces new serious issues to the systems. Proper support for responsibility and flexibility is a necessary precondition for solving the issues or for recovery from them. We cope with those issues by proposing software architecture simplifying alignment of software with responsibility domains. The solution is enabled by a proper application of specific software service types described here. The proposed solution significantly improves system and organizational flexibility and openness and brings many other interesting engineering advantages. The proposed solution is based on observations from human behaviour and roles within organizations and their cooperating groups.

This paper describes the analysis of dependability and predictive reliability. The proposed methodology is based on hierarchical models and the generally acclaimed standard MIL-HDBK 217F. The equipment is a real component of the railway interlocking system in Czech Republic. The equipment is designed for high dependability and with respect of disturbances caused by the near environment. A possible encapsulation using UML to model processes affecting the reliability is shown.

Modern trains must provide a certain level of control, diagnostic and information services. To satisfy it, rail vehicles have to be equipped with devices communicating over special networks. Nowadays, commonly used networks are described in the IEC 61375 and the UIC 556 standards. The National Train Bus (NTB) is a train network standard created in parallel with IEC 61375. The main difference is that it can operate on lower speed than it is common in rail environment, while still keeping the time-critical character of communication in mind. Therefore, it is suitable for rail vehicles, including refurbished ones, to avoid high requirements on installed hardware and software. It was successfully tested and it is being used in many different DMUs operated by Czech and Finnish Railways. This article describes the main communication and diagnostic principles of NTB and shows the differences between the IEC 61375 solutions and NTB.

This paper describes the dependability evaluation of track circuit receiver. The device is a component of railway interlocking system used in Czech Republic at conventional lines. The device is based on 2oo3 principle for high dependability. The reliability analysis, model and safety characteristics calculations of this device are described. Markov chain model is used for the reliability analysis.