Safety-Related Systems CTAL-TTA Practice Questions (Page 1)

Questions 1–5

1. 1expert · hard

   A company develops a railway signaling system classified as SIL 4 under IEC 61508. The project has a fixed deadline and limited test resources. The FMEA identifies two failure modes: Failure A has moderate severity but high occurrence; Failure B has catastrophic severity but very low occurrence. The test manager asks the Technical Test Analyst to allocate testing effort. What is the most appropriate approach?

   • APrioritize Failure A because its high occurrence means it will happen more often in the field.
   • BPrioritize Failure B because its catastrophic severity, combined with the SIL 4 context, demands the highest testing rigor.
   • CDefer testing for both failure modes until after the system is deployed and field data is collected.
   • DAllocate equal effort to both failure modes because both are safety-related.
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2. 2foundation · medium

   What is the primary purpose of establishing traceability in a safety-related system?

   • ATo track the version history of the source code.
   • BTo document the results of each test execution.
   • CTo record the time spent by each tester on each test case.
   • DTo ensure that every requirement is linked to design elements and test cases, demonstrating complete coverage.
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4. 3application · medium

   A safety auditor for an IEC 61508 SIL 2 system asks the test team to demonstrate that every safety requirement has been tested. The team has a requirements document, a design specification, and a test report, but no links between them. What is the most appropriate action for the Technical Test Analyst?

   • ACreate a traceability matrix that maps each safety requirement to its design element and corresponding test cases.
   • BRewrite the test report to include a summary of all safety requirements.
   • CPerform additional testing until all requirements are covered, without documenting the links.
   • DAsk the developers to confirm that all requirements were considered during coding.
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5. 4application · medium

   A team developing an ISO 26262 ASIL C airbag control unit wants to use an open-source code coverage tool to measure MC/DC. The tool is widely used but has no formal certification. What must the team do before using this tool in the safety lifecycle?

   • AUse the tool without qualification because open-source tools are exempt from ISO 26262 requirements.
   • BQualify the tool by providing evidence that it is suitable for use in the safety context, such as through a tool qualification report.
   • CReplace the tool with a commercial tool that has a certificate, regardless of cost.
   • DManually calculate MC/DC coverage for all code to avoid using the tool.
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6. 5foundation · medium

   Which element is typically included in a test report for a safety-related system?

   • AA summary of the test results and the achieved coverage criteria.
   • BA list of all possible failure modes of the system.
   • CA plan for future maintenance activities.
   • DA detailed description of the software architecture.
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