Verification and validation for a sub-system, making part of the On-Board Technological System (hereinafter referred to as STB), in regard to a serial head train so that this would be configured in accordance with the safety requirements - CENELEC Standard EN50128 "Railway Applications - Safety related electronic systems for signaling".

SCMT Project

SCMT is an electronic safety system aimed to protect the train march, moment by moment, with respect to: the conditions imposed by the signals, the maximum speed allowed by the railway line under normal conditions and in decay, the maximum speed allowed by the rolling stock. The system enables emergency braking in case of exceeding control speed limits. It is "transparent" to the driver that continues working in accordance to the general conduct rules.
The system is divided into the SST (Ground Subsystem) and the SSB (On-board subsystem).
The Ground subsystem consists, in its minimal configuration, of an encoder, generally located in the station. The encoder generates a telegram containing the range of information in accordance to the established protocol and basing on the conditions that the safety device provides. This telegram is transferred to a buoy (or BALISE), or to a TRANSPONDER placed on a side track, which is responsible of sending the telegram to the SSB. The set of two or more buoys installed on the railway line and transmitting the same information content, is called an Information Point or IP (duplication or redundancy is used to increase the system availability in case of failure of a single buoy). The buoy, which in almost in all cases is Eurobalise x 1023bit, is "energized" by the passage of the train’s antenna, thus transmitting the coded information.
Application Software verification activities (ASW)
The verification is essential to assess the completeness, consistency, security and traceability of such documents as [SWRS], [SWADS] and [SWDDS].

In particular, it is necessary to check:

• whether the SCMT-SSB requirements are properly tracked in SwRS
• whether the SwRS requirements are correctly traced in SwADS
• whether the SwRS requirements are properly tracked and implemented in DDS Sw

Input documents

• SRS: Software Requirements Specifications that define the requirements for SCMT-SSB
• SwRS, SwADS, SwDDS documents.

Output Documents

Verification Report: description of the checks carried out and of any fault found (along with the indication, if any, of a corrective action to be implemented).

Software validation activities

The SCMT software is composed of two main components:

• Application software: ASW, which handles and control the train movement
• Basic Software: BSW, which handles communication between various devices of SCMT and generation of necessary signals addressed to ASW

The ASW and the BSW are subject to separate but similar life cycles, according to the CENELEC 50128. The verification described in the preceding paragraphs refers to the ASW.
The validation should be reported, instead, to ASW + BSW.

The software validation activities, in accordance with CENELEC 50128, are necessary to determine the product quality & safety.

The results of the following items are being analyzed:

• control of the organizational framework adopted for the development of SIL 4 software
• control of all project documentation;
• both software and hardware configuration of the analyzed board
• critical review of the anomalies detected during the verification activities regarding the phases of the descending branch of the software life cycle
• critical review of the anomalies found during the verification activities of the phases of the ascending branch of the software life cycle
• functional control of software requirements, performed through a series of appropriate tests

Input documents

The following documents are provided in input:

• all the software project documentation
• all the software verification documentation
• all the software test documentation
• available Safety and Design Reviews

Output Documents

The Sw Validation Report is generated in output. This document reports the outcome of analysis carried out on all the incoming documentation and highlights the degree of quality and safety of the software product.

Tools Used

• Microsoft Word
• Microsoft Excel
• Microsoft Access
• Issue Tracker
• Clear Quest
• Simulators (if necessary for the test lab)

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