Human Factors in the Development of Safety-Critical Railway Systems

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Human Factors in the Development of
Safety-Critical Railway Systems

• Simon Zhang,
• Technical Director,
• Lloyds Register Rail (Asia) Ltd

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Factors affecting Safety Critical System
Development
1. Management systems and processes to safely
guide and control business activities
The Equipment
The System
2. Capable and competent people and culture to
deliver safety objectives
The People
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Human Errors in the Railway World

• Human errors can be costly and/or fatal

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System Lifecycle
Where do human errors occur in the development
lifecycle? What type of errors occur why? How
can they be addressed?
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Strategies for addressing Human Error in System
Development

• EN50126 Guidelines
• Human competency
• Human independence during design
• Human involvement in verification and validation
  (VV)
• Interface between human and automated tools
• Systematic failure prevention processes
• Application of EN50126
• Competency is a prerequisite
• Education and training are assumptions

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EN50126 Process Framework
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EN50129 View (1)

• Safety Organisation

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EN50129 View (2)

• Systematic failure prevention processes

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EN50129 View (3)

• Human Involvement in VV

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Limitations of Process-Based Standards

• Incompleteness of processes
• Inadequate guidance on human factors in system
  development
• Questionable rationale for SIL and Processes
• The processes for higher SIL may not produce
  safer products or systems
• Applicability of standards
• Well understood problem domain
• Risk totally covered
• Mature project and safety organisation

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Yellow Books View

• Compliance based approach
• Using existing standards as the driver to develop
  and evaluate a system
• Risk based approach
• Using risk assessment as the driver to develop
  and evaluate a system

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Assessors View (from LR Rail experience)
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Emerging Themes from Assessments

• Mainly from the Chinese railway signalling
  industry in recent 3 years
• 20 Chinese companies
• 30 RPC projects
• 10 ISA projects
• Aim to explicitly identify and evaluate the
  underlying risk associated with known human
  factors in system development
• Using EN50126/9 standards as a starting point
• Several themes emerged from the studies relating
  to human errors human factors

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Chinese Railway Signalling Industry

• China has experienced a large number of railway
  construction projects in both high speed mainline
  and metro systems
• Lessons from last years 7.23 railway accident
• Due to serious design flaws in control equipment
  and improper handling of the lightning strike
• Personnel competency is questionable
• Re-examine existing safety management systems and
  development processes

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Initial Findings Theme 1

• Human competency
• Undefined competence requirements on many roles
  such as verifier, validator and safety engineer
• Training and qualification records may not be
  trusted
• Certified or qualified training and education
  institutes are required
• Domain knowledge and experience are more
  important and can be easily verified via
  interviewing
• Organisational culture and HR policy can also
  influence
• Difficult to keep capable safety engineers

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Initial Findings Theme 2

• Human Independence during Design
• Organisational structures
• E.g. rigidly hierarchical structures
• Leadership patterns
• Two extremes
• Responsibilities and roles
• Incorrect understanding of allocated
  responsibilities and authority control

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Initial Findings Theme 3

• Human Involvement in VV
• Undefined competence requirements on many roles
  such as verifier, validator and safety engineer
• Lacking domain knowledge from the verifier or
  auditor
• Misunderstanding the role of VV
• Lack sufficient project resources for VV
  activities
• Tight project schedule

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Initial Findings Theme 4

• Interface between Human and Automated Tools
• Undefined competence requirements on the tool
  users
• Lacking of guidance on safety analysis over the
  tools
• Difficult to have a systems approach
• Viewing the tool and tool user as a complete
  system in a context of a project

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Initial Findings Theme 5

• Systematic failure prevention processes
• Inadequate guidance on techniques/measures
  recommended from standards
• linking techniques/measures with a level of
  recommendations does not help
• Tactic knowledge is required
• Undefined competence requirements on many roles
  such as verifier, validator
• Safety management system may also help
• But there is lack of guidance from the standards

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Enhancing assessments to evaluate human factors

• Is there good
• working culture?,
• leadership?
• motivation?
• Are roles, responsibilities authorities
  defined?

Can people reach everything? Is there enough
space to work? Are there obstructions? Can a good
working posture be achieved?
Can procedures be followed? Is there time
pressure? What working hours or breaks? What
training is given? What level of supervision is
there? What competence is required are these
well defined? Processes for using tools well
developed? Is there understanding of safety
standards?
Is the machine/tool easy to use? Is the behavior
of the tool understood by user? What happens if
the tool fails (e.g. during VV)? Is it available
where it is needed? Does the interface meet
expectations?
Is the lighting OK? Is noise a distraction or
does it prevent good communication? Does the
temperature make people tired?

• What attributes does a person need
• good vision/hearing,
• strength,
• particular skills,
• personality traits
• motivation?
• Qualifications experience
• Domain knowledge

How can we bring these into the assessments?
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Evolution of the Standards

• Introduction of EN501282011 Standard
• Definition of 10 roles including verifier and
  validator
• Guidance on support tool for software development
• Focus on tool validation and tool specification
• New development on EN50126/9 standards in the
  near future
• Merging the EN50126/8/9 standards together
• The role and competence requirements of safety
  engineer need to be defined
• More guidance on using the HR/R
  techniques/measures
• Develop guidelines on the SMS (safety management
  system)
• Interface between human and tools needs to be
  elaborated

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Future Work

• Get feedback on the viability and effectiveness
  of the approach
• Conduct more empirical studies from other
  geographical areas such as Hong Kong, Taiwan,
  Korea and India
• Define robust human factors evaluation framework
• Consider ranking or quantitative assessment
• Provide input to the development of new
  EN5016/8/9 standards
• Industry research into root causes of Human
  Errors during system design

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Conclusions

• Do not take human competency for granted
• Company/project management styles can always
  influence human independence
• Human judgement determines the VV success
  criteria
• Interface between human and automated tools can
  be unexpectedly complex
• Understanding the rationale behind
  techniques/measures is more important than
  choosing which in the systematic failure
  prevention processes.

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Finally

• Human error plays a part in most, if not all,
  accidents. If you have not considered human error
  when specifying your work, it will be difficult
  to show that you have controlled risk to an
  acceptable level.
• Human error has causes. We understand some of
  these and know how to prevent them. When
  designing railway systems you should look for
  opportunities to prevent human error leading to
  an accident.

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