The Role of Independent Safety Assessors (ISA) in Railways

Introduction

Safety is a critical aspect of railway projects, where failures can lead to severe consequences, including accidents, financial losses, and regulatory penalties. To ensure that railway systems comply with safety standards and operate reliably, Independent Safety Assessors (ISA) play a crucial role in evaluating and verifying safety processes. Their impartiality and expertise help identify risks and confirm that safety measures are adequate before a system is approved for operation.

Who are Independent Safety Assessors (ISA)?

An Independent Safety Assessor (ISA) is an entity or individual responsible for independently evaluating the safety aspects of a railway system, ensuring compliance with relevant standards and regulations. ISAs operate separately from the design, implementation, and operational teams to maintain objectivity.

Key regulations and standards that define the ISA role include:

CENELEC standards:

• EN 50126 (RAMS – Reliability, Availability, Maintainability, and Safety)
• EN 50128 (Software for railway control and protection systems)
• EN 50129 (Safety-related electronic systems for signaling)

What does an ISA do?

The primary responsibility of an ISA is to independently assess and verify safety throughout a railway project. Their tasks typically include:

• Reviewing safety documentation: Evaluating the Safety Case, hazard logs, and risk assessments to ensure they meet the applicable requirements.
• Verifying compliance: Checking that processes align with CENELEC, and other applicable safety standards.
• Assessing risk management: Ensuring that hazard identification, risk analysis, and mitigation measures are properly applied.
• Conducting audits and inspections: Reviewing project implementation and inspecting physical systems to validate compliance with safety principles.
• Providing independent opinions: Delivering unbiased safety assessments.

When is an ISA Required?

The need for an ISA depends on the phase of the railway project and on the Safety Integrity Level of the functions. In general, an ISA is required when:

• The project is in early phases of lifecycle (Phases 1 until 4) defined in EN 50126.
• The project is in later phases of lifecycle (Phases 5 until 12) defined in EN 50126 AND at least one function has SIL 1 or above.

In some cases, organizations may voluntarily engage an ISA to enhance safety assurance, even when not legally required.

Challenges and Best Practices

Common Issues Identified by ISAs

• Inadequate hazard identification: Missing or poorly defined hazards in risk assessments.
• Incomplete safety documentation: Gaps in safety cases, verification records, or traceability.
• Weak risk mitigation strategies: Insufficient evidence that risks have been reduced to an acceptable level.
• Non-compliance with standards: Deviations from regulatory requirements leading to project delays.

Best Practices for a Smooth ISA Assessment

• Involve the ISA early: Engaging an ISA from the start helps identify and address issues proactively.
• Maintain clear documentation: Ensuring that safety-related records are complete, well-structured, and traceable.
• Follow a structured safety process: Using established methodologies improves compliance.
• Foster collaboration: Effective communication between project teams and the ISA can streamline the assessment process.