CLC/TR 50126-3:2008

SLOVENSKI STANDARD
01-oktober-2008
1DGRPHãþD
SIST-TP CLC/TR 50126-3:2006
Železniške naprave - Specifikacija in prikaz zanesljivosti, razpoložljivosti,
vzdrževalnosti in varnosti (RAMS) - 3. del: Vodilo za uporabo EN 50126-1 za RAMS
za vozna sredstva
Railway applications - The specification and demonstration of Reliability, Availability,
Maintainability and Safety (RAMS) - Part 3: Guide to the application of EN 50126-1 for
rolling stock RAM
Applications ferroviaires - Spécification et démonstration de la Fiabilité, de la
Disponibilité, de la Maintenabilité et de la Sécurité (FDMS) - Partie 3: Guide pour
l’application de la EN 50126-1 à la fiabilité, la disponibilité, la maintenabilité et la sécurité
du matériel roulant
Applications ferroviaires - Spécification et démonstration de la Fiabilité, de la
Disponibilité, de la Maintenabilité et de la Sécurité (FDMS) - Partie 3: Guide pour
l’application de la EN 50126-1 à la fiabilité, la disponibilité, la maintenabilité et la sécurité
du matériel roulant
Ta slovenski standard je istoveten z: CLC/TR 50126-3:2008
ICS:
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
45.020 Železniška tehnika na Railway engineering in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CLC/TR 50126-3
RAPPORT TECHNIQUE
July 2008
TECHNISCHER BERICHT
ICS 29.280; 45.020 Supersedes CLC/TR 50126-3:2006

English version
Railway applications –
The specification and demonstration of
Reliability, Availability, Maintainability and Safety (RAMS) –
Part 3: Guide to the application of EN 50126-1
for rolling stock RAM
Applications ferroviaires –  Bahnanwendungen –
Spécification et démonstration de la Spezifikation und Nachweis der
Fiabilité, de la Disponibilité, de la Zuverlässigkeit, Verfügbarkeit,
Maintenabilité et de la Sécurité (FDMS) – Instandhaltbarkeit, Sicherheit (RAMS) –
Partie 3: Guide pour l’application de la Teil 3: Leitfaden zur Anwendung der
EN 50126-1 à la fiabilité, la disponibilité, EN 50126-1 für Bahnfahrzeuge RAM
la maintenabilité et la sécurité du matériel
roulant
This Technical Report was approved by CENELEC on 2008-05-09.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TR 50126-3:2008 E

Foreword
This Technical Report was prepared by Working Group B11 of SC 9XB, Electromechanical material on
board of rolling stock, of Technical Committee CENELEC TC 9X, Electrical and electronic applications for
railways.
The text of the draft was submitted to the vote and was approved by CENELEC as CLC/TR 50126-3
on 2008-05-09.
This Technical Report supersedes CLC/TR 50126-3:2006.
This Technical Report forms an informative part of EN 50126 and contains guidelines for the application
of EN 50126-1 to Rolling Stock RAM.
__________
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Contents
Page
Introduction . 6
1 Scope . 7
2 Definitions . 7
3 Approach adopted for the Guide. 8
3.1 General. 8
3.2 Entities Involved In the Life Cycle Phases of Rolling Stock . 8
4 Application of this Guide . 8
4.1 Object of the application. 8
4.2 Application of EN 50126-1 . 9
4.2.1 Assessment of the application of EN 50126-1 . 9
4.2.2 Mandatory requirements for the application of EN 50126-1 . 9
5 Specifying RAM requirements . 10
5.1 Introduction . 10
5.2 Preliminary RAM analysis . 10
5.2.1 General . 10
5.2.2 Preliminary RAM Analysis activities. 10
5.2.2.1 General . 10
5.2.2.2 System Identification . 11
5.2.2.3 Breakdown structure and boundary limits . 12
5.2.2.4 Failure Conditions . 14
5.3 RAM requirements . 16
5.3.1 Introduction . 16
5.3.2 Reliability Targets . 16
5.3.3 Maintainability Targets . 18
5.3.3.1 Generic Qualitative Requirements for Maintainability . 18
5.3.3.2 Preventive/Corrective Maintenance Requirements . 20
5.3.3.3 Logistic Support Requirements . 20
5.3.3.4 Maintenance Cost Requirements . 21
5.3.4 Availability Targets . 21
5.4 Process for choosing RAM figures . 24
5.5 RAM Programme . 24
5.5.1 Introduction . 24
5.5.2 Configuration Management System . 25
5.5.3 RAM Programme Outline . 25
5.5.4 Example of RAM Analyses Document Template and Data . 26
5.5.4.1 Introduction . 26
5.5.4.2 Common Data for the analyses . 26
5.5.4.3 Reliability Prediction Analysis Template and Data Sheets . 27
5.5.4.4 Maintenance Attributes (Maintenance Levels, Skill Level and LRU definition) . 29
5.5.4.5 Preventive Maintenance Analysis Template and Data Sheets . 31
5.5.4.6 Corrective Maintenance Analysis Template and Data Sheets . 35
5.5.4.7 Failure Mode Effects and Criticality Analysis Template and Data Sheets . 37

6 RAM Assurance during Life Cycle . 40
6.1 RAM Programme and Phases of the Life Cycle . 40
6.1.1 Introduction . 40
6.1.2 Tender Phase . 41
6.1.3 Design Phase . 42
6.1.4 Demonstration Phase . 44
6.1.4.1 Introduction . 44
6.1.4.2 RAM Acceptance Criteria . 45
6.1.4.3 In service checking Period . 45
6.1.4.4 Data Report from field and its organisation . 46
7 RAM Parameters to be incorporated into LCC Model . 47
7.1 Introduction . 47
7.2 Overview of LCC Modelling . 47
7.3 RAM parameters for LCC. 48
Annex A Examples of breakdown structure . 49
Bibliography . 62

Figures
Figure 1 – Example of Reliability Prediction Analysis Sheet . 28
Figure 2 – Example of Preventive Maintenance Analysis Sheet . 32
Figure 3 – Example of Preventive Maintenance Sheet for a single frequency . 34
Figure 4 – Example of Corrective Maintenance Analysis Sheet . 36
Figure 5 – Example of items FMECA Sheet . 38
Figure 6 – Example of functions FMECA Sheet . 39
Figure 7 – RAM Programme and Life Cycle Phases . 40
Figure 8 – Possible relationships between Customer, Main Supplier, Sub-Supplier during some
phases of Life Cycle for rolling stock . 41
Figure 9 – Flow diagram representing activities/documentations of Design Phase. 42
Figure A.1 – Example of physical structure using organisation chart for an Electrical Multiple Unit
Coach . 50
Figure A.2 – Example of functional structure using organisation chart for an Electrical Multiple Unit
Coach . 51
Figure A.3 – Example of structure using the tree breakdown chart for an EMU (Electrical Multiple Unit)
Traction Vehicle . 58
Figure A.4 – Example of structure using the tree breakdown chart for an EMU (Electrical Multiple Unit)
Coach . 61

- 5 - CLC/TR 50126-3:2008
Tables
Table 1 – Possible sharing of responsibility . 8
Table 2 – Example of minimum set of data of the header for a form representing a breakdown
structure . 13
Table 3 – Example of minimum set of data representing a breakdown structure . 14
Table 4 – RAM Failure Categories . 14
Table 5 – Significant Failure Specification . 15
Table 6 – Major Failure Specification . 16
Table 7 – Minor Failure Specification . 16
Table 8 – Reliability Requirements for Failure Categories . 17
Table 9 – Qualitative Requirements for Maintainability . 18
Table 10 – Preventive/Corrective Maintenance Requirements . 20
Table 11 – Logistic Support Requirements . 20
Table 12 – Maintenance Cost Requirements . 21
Table 13 – Availability Requirements . 23
Table 14 – Example of minimum set of data of the header for RAM analyses Template . 27
Table 15 – Example of minimum set of data for Reliability Prediction sheets . 27
Table 16 – Example of minimum set of data for Preventive Maintenance sheets . 31
Table 17 – Example of minimum set of data for Corrective Maintenance sheets . 35
Table 18 – Example of minimum set of data for items FMECA sheets . 37
Table 19 – Description of the main tasks of Design Phase . 43

Introduction
EN 50126-1 is likely to enhance the general understanding of the issues involved in achieving RAMS
characteristics within the railway field. It defines a comprehensive set of tasks for the different phases of a
generic life cycle for a total rail system. Although some of the examples given in the annexes of
EN 50126-1 are for rolling stock, the standard is essentially aimed as a top level railway system
document.
RAMS characteristics for rolling stock (i.e. its long term operating behaviour performance), as for any
other system, forms an important part of its overall performance characteristics. But the consideration of
RAMS, in contractual terms, between a customer / operator and a Main Supplier for the procurement of
rolling stock has been problematic. Also, in rolling stock contracts, there is now a greater emphasis on the
impact on end customers of service failures and on the economic and risk considerations of RAMS
(i.e. the business perspective).
Consequently, Life Cycle Cost is being used as a measure of satisfying customer needs and providing a
wider perspective of RAMS importance in terms of the business economics.
Life Cycle Cost approach represents a holistic, total cost of ownership philosophy for addressing the
economic considerations. The contribution of RAMS to the LCC (Life Cycle Cost) of rolling stock could be
used to allow the economic considerations to be addressed.
This application guide focuses mainly on the tasks and issues from procurement, engineering and
maintenance, from the tender to the operation/maintenance phase, and is intended to help in establishing
a common approach for capturing the different, time dependant, performance requirements of rolling
stock from an operator/business perspective.
EN 50126-1 is a standard, which treats the overall aspects of RAMS in Railway Applications.
This guide deals with the application of RAM part of EN 50126-1 to rolling stock only, as stated in the
Scope and clarifies areas where EN 50126-1 could be misinterpreted.

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1 Scope
This document provides guidance on applying the RAM requirements in EN 50126-1 to rolling stock and
for dealing with RAM activities during the system life cycle phases from invitation to tender to
demonstration in operation only. All references to EN 50126-1 concern the version of 1998.
The guide is aimed at the customers/operators and main suppliers of rolling stock. The main purpose of
the guide is to:
• enable a customer/operator of rolling stock:
− to specify the RAM requirements addressing the type of operation in terms of the end customer
needs, considering service availability and economic considerations;
− to evaluate different tenders, in terms of RAM requirements, on a common basis with the aid of
specific RAM documents;
− to gain assurance, during design/development phase, that the rolling stock being offered is
likely to satisfy the RAM contractual requirements by examining step by step detailed and
specific RAM documents as an output of the RAM activities performed during the development
phase;
− to validate that the rolling stock, as delivered, satisfies the specified RAM requirements
• to enable the main supplier of rolling stock
− to understand the customers/operators RAM requirements
− to provide substantive information/visibility in a tender to show that the product offered is likely
to satisfy the RAM requirements by performing preliminary RAM analysis;
− to provide substantive information during design/development phase to show that the product
offered is likely to satisfy the RAM requirements by performing detailed RAM analysis;
− to demonstrate that the product delivered satisfies the RAM requirements;

Regarding LCC, this application guide is restricted to providing only the key RAM parameters necessary
to be incorporated into an LCC Model.
This application guide excludes:
• RAM values connected to the different RAM requirements (however, it contains a simple guide line
of actions for supporting the decision making process and choosing appropriate values, see 5.4)
• specific RAM documents to be produced and activities to be performed. However, it provides, only
as an example, typical data and document templates for recording the output of a RAM analysis).

2 Definitions
For the purposes of this document, the terms and definitions given in EN 50126-1 and the following apply:
2.1
Part Number
the alphanumeric code, generally assigned by the Main Supplier, to represent a family of items with the
same characteristics of Form, Fit and Function

3 Approach adopted for the Guide
3.1 General
The approach adopted is to raise the following questions, for each phase of the Life Cycle, in order to
successively set up the requirements of EN 50126-1 and the basis for satisfying them:
• WHAT: what activities / tasks are to be performed and the supporting documents to be produced?
• WHO: who has the responsibility for these activities / tasks?
• HOW: which type of method or tool should be used?
This process is adopted for the development of the guide and should be applied in accordance with the
structure of the application guide.
3.2 Entities Involved In the Life Cycle Phases of Rolling Stock
Depending on the organisational and management structure of the railway system concerned, a number
of entities, performing different functions, may be involved within the life cycle phases of rolling stock. For
the purpose of guidance on contractual relations, the entities are divided into 2 main categories, i.e.
customer and supplier.
It is therefore advisable, to identify all the entities that can be a part of this relationship and to examine
how the responsibilities of dealing with these entities are shared between the customer and supplier
relationship. Table 1 gives some typical examples only:
Table 1 – Possible sharing of responsibility

Supplier
Customer
Entity
responsibility
responsibility
Main supplier of the rolling stock X
Sub supplier of the rolling stock X
Operator of the rolling stock X
Owner of the rolling stock X
Maintainer of the rolling stock X X

4 Application of this Guide
4.1 Object of the application
This document is applicable to rolling stock (train, coach, locomotive, etc…) and to all the subsystems,
assemblies and parts belonging to the rolling stock, according to their boundary limits.
Referring to 1.2 of EN 50126-1, the Guide is for use by Railway Authorities and the railway support
industry and is applicable to:
• new rolling stock,
• modification/refurbishment of existing rolling stock.
For use in this document only, the above two bullet point items should be referred to by the generic term
“system”, comprising the complete sequence “system, sub-system, component” of a rolling stock or the
whole rolling stock itself breakdown structure.

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4.2 Application of EN 50126-1
4.2.1 Assessment of the application of EN 50126-1
Referring to 5.3 of EN 50126-1 and taking into account the responsibilities of the different entities involved
in the life cycle phases, the following subclause gives a synthesis of the main actions required to meet the
requirements.
According to 5.3.2 of EN 50126-1, the assessment of the application of the requirements of EN 50126-1
to rolling stock (system under consideration) shall be defined by the Railway Authority and according to
5.3.4 of EN 50126-1, the assessment shall:
1 Specify phases applicable, and for each one of these:
• Justify and demonstrate the compliance with the principles of the requirements of the standard;
• Specify the mandatory activities/requirements, with respect to rolling stock (system under
consideration), including:
I. The scope of each requirement,
II. The methods, tools and techniques required against each requirement and the scope
and depth of their application,
III. The verification/validation activities required against each requirement and the scope
of their application,
IV. Input/Output documentation;
2 Justify any deviation from the activities and requirement of the standard;
3 Justify the adequacy of the tasks chosen for the system under consideration.
Both the Customer and the Main Supplier should provide documented evidence for the above
specifications and justifications that are within their responsibility.
Where Main Supplier introduces limitations, they should be discussed and agreed with the Customer.
These documents are considered as part of the RAM Programme.
4.2.2 Mandatory requirements for the application of EN 50126-1
The correct application of EN 50126-1 is effected through several requirements.
The following is a synthesis of the mandatory requirements in 5.3.5 of EN 50126-1 regarding RAM only:
• define and agree the responsibilities for carrying out all RAM tasks within each phase chosen;
• ensure the competence of the personnel involved within RAM tasks;
• establish and implement a RAM Programme, where the following should be identified and managed:
− conflicts between RAM and Safety tasks,
− details of all RAM analysis, including the depth of analysis activities;
• ensure that the requirements of EN 50126-1 are implemented within business processes, supported
by a Quality Management System (QMS) compliant with the requirements of EN ISO 9000 series;
• establish and implement an adequate and effective configuration management system including, at
least:
− all system documentation,
− all other system deliverables.
Both the Customer and the Main Supplier should provide evidence by documents about the fulfilment of
these mandatory requirements, within their responsibility.
These documents are considered as part of the RAM Programme.

5 Specifying RAM requirements
5.1 Introduction
The purpose of this clause is to establish the process to define RAM Requirements for rolling stock and
for all the subsystems, assemblies and parts belonging to the rolling stock according to its boundary
limits.
This clause gives detailed information on phases 1, 2, 4 and 5 of system life cycle requirements
described in 6.1, 6.2, 6.4 and 6.5 of EN 50126-1.
To start with, as part of the system definition process, all available data and relevant information about
the rolling stock under consideration should be collected.
The final goal is the derivation of RAM targets through the appropriate analysis of all the information
collected and organised in a structured way.
5.2 Preliminary RAM analysis
5.2.1 General
This subclause complements 6.1.3.4, 6.2.3.1, 6.2.3.2, 6.4.3.1 and A2 of EN 50126-1 and gives further
details.
Purpose of the preliminary RAM Analysis is to identify the application environment and the operating
conditions of the rolling stock, in order to recognise the fundamental concepts for basing the overall RAM
requirements.
The analysis involves undertaking the following activities:
• similar system review:
− a list of similar existing rolling stock is created, suitable for extracting relevant RAM-related
information;
• preliminary system analysis:
− all available and relevant rolling stock documentation is reviewed in order to define, at a
preliminary level, the overall system structure and its mission profile and to recognise the
system failure conditions.
Deliverables of the preliminary RAM-related activities constitute the necessary background for defining
the overall RAM Requirements Specification in terms of:
• RAM requirements;
• Demonstration and acceptance criteria;
• RAM programme requirements.
5.2.2 Preliminary RAM Analysis activities
5.2.2.1 General
Preliminary RAM-related activities consist of investigating all the relevant available documentation in
order to recognise all the functional requirements, which may affect the RAM performance of the rolling
stock.
The resultant deliverables of the preliminary RAM-related activities are:
• System identification: where the rolling stock has to be identified in terms of its boundary limits,
operational conditions, functions, interfaces, system breakdown structure, logistics and maintenance
conditions.
• Failure conditions: where the failures of the rolling stock have to be identified and categorised in
order to define appropriate requirements.

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5.2.2.2 System Identification
This subclause provides a general overview of the main features identifying a rolling stock (see
EN 50126-1, Clause A.2).
The identification process is carried out to gain assurance that the rolling stock is correctly analysed and
all the factors influencing its RAM performance have been identified.
These characteristics define the conditions under which the rolling stock is required to accomplish its
mission and constitute the reference conditions for:
• defining the rolling stock RAM requirements;
• demonstrating, by analysis and tests, that each specific implementation fulfils the RAM requirements
in all relevant Lifecycle phases.
The main characteristics and features necessary to describe a rolling stock are its Mission Profile, Route
Profile, Operating Conditions, Environmental Conditions and Maintenance Conditions (including logistics).
Items contained in each of these are listed below:
1 Mission Profile:
• Reference route,
• Commercial speed (mission duration / mission length),
• Mean length of a run,
• Mean distance between train stops,
• Operating time or distance per year,
• Revenue operating time or distance per year,
• Stand-by time per day,
• Idle time per day (i.e. time when the rolling stock is neither in operation nor stand-by),
• Planned total time of use (life expectancy in years).
2 Route Profile:
• Number of tunnels related to reference route,
• Number of viaducts related to reference route,
• Cumulative distance in tunnels,
• Cumulative distance on surface, including viaducts,
• Gradients and curves on the route with their lengths.
3 Operating Conditions:
• Equivalent speed related to the time the equipment is powered during a given calendar period
(cumulated distance / Time the equipment is powered over the period),
• Time an equipment is powered over a given calendar period (this parameter could be defined
for each equipment, but is generally defined for categories of equipment),
• Time during which traction is activated,
• Time or percentage of time during which electric braking is activated,
• Operating time of the compressor,
• Number of compressor startups,
• Time of presence of catenary power, for each voltage,
• Time during which a trainset is awake (i.e. in operation or standby),
• Operating time for Heating Ventilation and Air Conditioning, in heating mode and in air
conditioning mode,
• Average speed and maximum speed,

• Potential use in multiple units,
• Total time of coupled operation,
• Frequency of coupling and de-coupling,
• Internal temperature range of the rolling stock,
• Mechanical (shock and vibration),
• Electrical (power supplies),
• Electromagnetic compatibility (e.g. EMC – train to train or system to system),
• Signalling interfaces (e.g. on-board and way-side),
• Ergonomics.
4 Environmental Conditions:
• Outside air temperatures (OAT),
• Maximum height above the sea level,
• Solar radiation,
• Humidity,
• Wind and pressure pulses,
• Water and precipitation,
• Pollutants and contaminants,
• Resistance to corrosion.
5 Maintenance Conditions:
• Indicative maintenance plan (i.e. minimum preventive maintenance interval, maximum
contemporary number of personnel required for maintenance interval tasks, maximum standstill
time to complete maintenance interval tasks, etc…),
• Number, location and description of the sites for maintenance,
• Description of the standard equipment, tools and resources at the maintenance sites.
5.2.2.3 Breakdown structure and boundary limits
5.2.2.3.1 General
Breakdown structure of the rolling stock is the most important baseline of the identification process.
Establishing a breakdown structure of the rolling stock, gives a clear reference outline for all the activities
and analyses for supporting RAM Programme through the Life Cycle.
Generally, the scope of the breakdown structure is to set up the borders of a system by listing all the
items belonging to that system and, by using an appropriate number of discrete breakdown levels for the
system, to draw out the relationships existing between the different items of the rolling stock.
There are two categories of structures to support RAM analyses:
• Functional breakdown structure,
• Physical breakdown structure.
The functional breakdown is used to perform preliminary criticality analyses. The last functional level
allows consequences of functional failure modes to be developed and the next physical level allows the
critical item list to be developed.
The physical breakdown is used to perform maintainability analyses. The last level of this breakdown is
the LRU (Line Replaceable Unit), as defined in 5.5.4.4. This breakdown is sometimes called the logistic
breakdown structure.
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5.2.2.3.2 Common rules to set up a physical breakdown structure
For setting up a breakdown structure, a decomposition process is carried out starting from the first level to
the other levels identified and being able to represent all the items and their functional relationships.
The decomposition process is based on a hierarchical breakdown in a top down process commencing
with the Rolling Stock as the system under consideration.
At each level identified in the hierarchy, every system identified becomes the next system under
consideration and can be further decomposed into lower levels, as necessary.
There are several methods and tools to set up a breakdown structure. The following are
recommendations to be followed in order to develop an appropriate and suitable breakdown structure for
RAM purposes:
• Avoid the use of "large number of levels" and limit these to a reasonable number (three or four are
suggested),
• Last item identified along a branch must be a LRU,
• Force the use of the same terms and definitions for identical items,
• Ensure that the terms and definitions used for every item are the same in all the design documents
(drawings, outlines, diagrams, specifications, etc…),
• After the first issue of the structure avoid continuous modifications,
• Avoid the use of vague or unclear definitions.
The definition used for LRU is well explained in 5.5.4.4.
5.2.2.3.3 Data to identify the physical breakdown structure
Every breakdown structure must be presented together with a set of drawings, diagrams, and functional
outlines in order to meet the target of identifying the Rolling Stock and all its subsystems, assemblies and
parts, clarifying at least:
• all the relationships between the items of the breakdown structure,
• the functional borders between different systems, subsystems, assemblies.
A minimum set of data is used to represent and to manage the breakdown structure.
This kind of data is the baseline of the different analyses that should be carried out during the Life Cycle.
Every breakdown structure should be represented with a header containing at least the following:
Table 2 – Example of minimum set of data of the header for a form representing a breakdown
structure
Subject Details
Rolling stock ID code or definition of rolling stock
Doc.N. Code of document
Version Number Number to identify the version of the document
Date Date of document referred to the version of the document
Page n/N Consecutive number of page/total number of pages
Drawn up by First and last name of author
Filename Name of file of the document
The following are the minimum set of data to represent a breakdown structure:

Table 3 – Example of minimum set of data representing a breakdown structure
Subject Details
Code Breakdown level code of the item
Description Description of the item
Qty Amount of the item under consideration in the higher level item
Part No. Part No. of the item
NOTE 1  The use of quantity information is suggested for breakdown structure where the product is defined.
NOTE 2  As appropriate, it is recommended the use of the Part Number for every item of the breakdown
structure.
Examples of Breakdown Structure are given in Annex A.
5.2.2.4 Failure Conditions
This subclause complements 4.5.2.2 and 6.4.3.2 of EN 50126-1 and gives further details.
The following general failure conditions are defined for the rolling stock based on general failure
categories, which may be experienced by a generic railway transport:
• Immobilising failures,
• Service failures,
• Minor failures.
Table 4 shows the Failure Categories indicated in EN 50126-1 and defines them in terms of their
application to rolling stock.
Table 4 – RAM Failure Categories
Failure Category Definition
A failure that:
Significant - prevents train movement or causes a delay to service greater than a
specified time and/or
(Immobilising Failure)
- generates a cost greater than a specified level
A failure that:
- must be rectified for the rolling stock to achieve its specified
Major
performance and
(Service Failure)
- does not cause a delay or cost greater than the minimum threshold
specified for a significant failure
A failure that:
Minor - does not prevent rolling stock achieving its specified performance and
- does not meet criteria for Significant or Major failures
In order to better define the above mentioned Failure Categories the following conditions are applicable to
Rolling Stock and to all its subsystems, assemblies and parts:
• Significant Failure (Immobilising Failure): Any failure occurring on Rolling stock and leading, at least,
to one of the following conditions:
− A delay greater than a specified time,
− Train stopped on the track,
− Train not allowed to enter service,

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− Withdrawal of the train from service,
− A cost greater than a specified threshold,
• Major Failure (Service Failure): Any failure occurring on the Rolling Stock and leading, at least, to
one of the following conditions:
− A delay less than a specified time,
− Loss of specific functions or their performance threshold falling below the specified minimum
acceptable level,
− A cost less than a specified threshold.
• Minor Failure:
− Any failure occurring on the Rolling Stock, that is not classified as significant or major, leading to
a maintenance task, even if this failure has no impact on service.
According to the above mentioned definitions and conditions of failures, the Customer should state:
• The number of minutes of delay for Significant Failures and Major Failures,
• The threshold cost for Significant Failures and Major Failures,
• The method for counting the delay (i.e. at the end of the run only, cumulated during all the stops, the
maximum between two stops, etc.),
• Specific service conditions which are deemed to result in stopping the train on the track or
withdrawing the train from service in case of Significant Failure,
• Functions and their performance thresholds, which are deemed to be classed as Major Failures (e.g.
the failure of the passenger air-conditioning, the failure of driver’s cab air-conditioning, the failure of
door system per side, the failure of a specified number of toilet system, the failure of the coach
lighting system, etc.).
Tables 5 to 7 show the specifications for each Failure Category.
Table 5 – Significant Failure Specification
Failure Threshold
Conditions Specification Requested
Category dimension
Delay greater than
Time Specify mode of counting delay
or
Train stopped on the track
Rolling Stock unable to proceed

under its own power.
or
SIGNIFICANT
Specify special service conditions
Withdrawal of the train from
(Immobilising
under which the Customer decides
service/Train not allowed to
Failure)
that the train is withdrawn from
enter service
service or stopped from entering
Fail
I
or
service
Cost greater than Money Specify reference cost

Table 6 – Major Failure Specification
Failure Threshold
Conditions Specification Requested
Category dimension
Delay less than
Time Specify mode of counting delay
or
Specify services/functions and
MAJOR
their performance threshold
Failing specified performance
levels below which the
(Service
or
Customer considers it as
Failure)
service failure
Fail
S
Cost less than Money Specify reference cost

Table 7 – Minor Failure Specification
Failure Threshold
Conditions Specification Requested
Category dimension
MINOR Any failure occurring on the

Time
Fail rolling stock
M
It should be noted that one or more conditions for each table of failure category might be applied.
5.3 RAM requirements
5.3.1 Introduction
This subclause complements 4.5.2.2 and 6.4.3.2 of EN 50126-1 and gives further additional details.
The aim of this subclause is to give an overview of the most commonly used RAM requirements in order
to help the Customer choose the most appropriate requirements for his rolling stock, and also take into
account any possible legal requirements, when existing.
In choosing the appropriate RAM Requirements, the Customer is strongly advised to consider the
following:
• System identification characteristics (mission profile, operating condition, function requested, etc…),
• Economic implications,
• Practicalities of being able to measure RAM performance from his field operations, depending on his
organisational and logistical structure and service procedures.
The Customer should document his process for choosing RAM Requirements stating the consideration
given to address each requirement chosen.
5.3.2 Reliability Targets
This subclause provides guidance on description of Reliability Targets required for the Failure Categories
Significant (Immobilising), Major (Service) and Minor Failure. (i.e. MTBF in Hours, failure rate per million
hours, or failure rate per million kilometres).
The Reliability Targets are applicable to the total rolling stock and all its subsystems, assemblies and
parts according to the boundary limits defined.

- 17 - CLC/TR 50126-3:2008
Using the above definition the Customer should specify the Reliability Targets for each one of the Failure
Categories in terms of:
• Maximum accepted Failure Rate,
• Minimum accepted MTBF/MTTF/MDBF.
The terms hours/kilometres represent hours/kilometres of service.
MTBF requirement is intended for repairable units and MTTF is intended for non-repairable units.
If the real service operating time for the rolling stock and for its subsyste
...