Page 73 - 捷運技術 第43期

捷運技術半年刊 第43 期 67

4eConclusion

A particular advantage of the CENELEC standards is that, due to EN 50126, RAM and safety

activities are handled jointly, also from the point of view of RAMS management. EN 50128 and

50129 give quantitative and qualitative rules to gain a Safety Related Software and to manage the

product developing phase for Signalling Systems. They also providing rules for demonstration

phase (50129) allowing to guarantee a wide range of Safety. Safety integrity requirements are finally

defined at a functional level. Moreover the CENELEC standards provide a structured approach
and flexible methodology for the achievement and demonstration of the system safety of complex

rail systems. Both, the integration of proven techniques and methods, as well as the analysis and

evaluation of new technologies, is easily possible and meaningful.

More benefits are listed below:

hSystematic process to define, implement and follow up on a safety process.

hTraceability of activities performed.

hStepwise process allows minimization of risks.

hGuidelines for demonstration phase allow to guarantee a wide range of Safety.

h Safety integrity requirements defined at a functional level giving a clear view of each safety
function and which subsystems are involved in.

hModularity and Portability of the approach.

Finally also in the US and in Asia the interest in the European norms has greatly increased

since they are likely to become worldwide IEC standards in the near future by a fast-track

procedure, making them the first worldwide standards in this field.

Reference

1.c U.S. Department of Defense (Feb 2000), “MIL-STD-882D, Standard Practice for System

Safety” (Superseding 882C), U.S. Military Standards.

2.c CENELEC EN 50126, The specification and demonstration of Reliability, Availability,

Maintainability and Safety (RAMS), CENELEC (1999-09).

3.c CENELEC EN 50128, Communications, signalling and processing systems - Software for

railway control and protection systems, CENELEC (2002-04).