Functional Safety in transport systems

Dec 12, 2019 / by GM International

Topics: Functional safety

The issue of safety in transport systems is highly complex and varied. Today, the safety and reliability requirements in any transport sector are strategic factors and functional safety is a key component thereof.

The increasingly frequent adoption, in means of transport, of computer systems and automation has raised safety issues to a level of greater complexity. Currently, when developing a transport system, safety is closely interconnected with the requirements of functionality, system costs and respect for the environment. Another aspect to consider is that the term "safety" in transport takes on different meanings, from the identification of possible risks to accident-prevention measures, all the way through to the concept of Functional Safety which, being of a generic nature, can also be applied to domains other than those typically found in the process industry.

In the transport sector, functional safety methods and standards form part of a broader framework that includes human factors, reliability and the evolution of technologies, risk management, data analysis and socio-economic assessments. Functional safety engineering – based on IEC 61508 and the standards derived from it – involves identifying specific hazardous failures and then establishing maximum tolerable frequency targets for each mode of failure.


Road transport

In the past, functional safety in the automotive sector was covered by the generic standard IEC 61508. With the publication of the industry-specific standard ISO 26262, the specific requirements of the automotive sector in the context of programmable electrical/electronic components (E/E) are addressed more adequately. The ISO 26262 standard can be used to apply a safety-management system based on internationally-recognized best practices, together with an innovative approach to risk management. Automakers are also about to start using ISO 26262 compliance as a means to qualify components and potential suppliers of E/E components. Associated with this standard, the Automotive Safety Integrity Level (ASIL) expresses the level of risk reduction of a safety function used in a given product. It is classified into four levels, from ASIL A to ASIL D, from the least to the most stringent level of risk reduction.


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Rail transport

The key areas for functional safety in the railway sector are tunnel safety systems, signalling systems and on-board train safety systems. Functional safety has become even more important as a result of European directives on railway interoperability and other regulations in the railway and metro network sector, which require verification of functional safety according to the EN 50126 (RAMS), EN 50128 (Software), and EN 50129 standards.

Equipment whose malfunction would result in the occurrence of each identified hazardous situation is identified and described as “safety-relevant”. Typical examples are railway signalling systems, equipment for platform screen doors, equipment release of extinguishing agents in the event of carriage fires.

The most widely-used methods include functional safety and software management, RAMS analysis, CTA (consequence tree analysis), FMEA/FMECA (failure mode analysis), PHA, SHA, SSHA, Hazard Logs, Hazop, IHA (hazard analysis), maintainability analysis and safety case processing.


Maritime transport

The maritime sector has a technical, operational and regulatory safety framework that is among the most complex and accurate in existence. Indeed, since 1 July 2004, all ships must have an International Ship Security Certificate (ISSC) and a Ship Security Plan (SSP). Ships must also be equipped with special Automatic Identification System (AIS) equipment for automatic identification by ground stations, both short-range and when they are at a considerable distance from land (over 200 nautical miles)°; ships must also have specific alert facilities (Ship Security Alert System).

Functional safety in the naval sector plays an important role in protecting against the risk of physical injury or damage to health, as well as indirect threats to property or to the environment. Assessment of functional safety for products and systems installed in maritime transport systems includes Hazard Analysis with identification of the safety functions and determination of the Target SIL, drafting of Safety Manuals with verification of the correct exportation of the application safety conditions and environmental operating conditions and Proof Test procedures.


Air transport

The operational safety of air carriers and their aircraft is ensured by a set of national and international rules and by checking that the above rules are adhered to. Automation in the aeronautical field consists of hardware and software systems that handle interconnected functions. An approach based on the functional safety of such systems ensures that the risks associated with hazardous situations caused by system malfunction, which can cause significant safety consequences, are kept down to acceptable levels.

Particularly relevant in this area are the supranational regulations that require the adoption of the Safety Management System (SMS) which in the civil aviation system have to be implemented by civil aviation and by all companies operating in the vast sector of air transport. The operating tools for SMS are hazard identification, risk analysis and assessment, risk mitigation to tolerable levels, measurement of the effectiveness of actions taken.



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