Key standards
- EN 50126/8/9 (RAMS and signalling), IEC 61508 (functional safety), ISO 13849 (machine safety), relevant AASHTO bridge codes.
Documented issues
- Rail signalling: On the Cambrian Coast line, the ERTMS/ETCS system lost temporary speed restriction data after a restart. The display still indicated the restriction was loaded. RAIB found there was no clear definition of “safety‑related data,” a single point of failure, and an Independent Safety Assessor failed to identify design-documentation issues. gov.uk.
- Bridge design: The FIU pedestrian bridge collapsed because FIGG Bridge Engineers made calculation errors in load and capacity, and peer review did not catch them; large cracks were ignored and retensioning constituted a design change requiring independent review. constructiondive.com.
Typical challenges
- Incomplete verification of safety-critical software and data; inadequate backup or error logging.
- Design calculations and peer review processes fail to identify overstress or changes.
- Poorly defined responsibilities among contractors and safety assessors.
Best Practice playbook
- Implement robust safety management and RAMS processes for high‑integrity software (EN 50126/8/9): define safety‑related data, use redundancy, and capture diagnostic data. gov.uk.
- Independently review and validate calculations for bridges and tunnels; any design change requires new checks. constructiondive.com.
- Monitor warning signs (e.g., cracks); treat them as potential failure indicators and follow emergency procedures.
- Document and audit all safety case assumptions and test evidence; ensure the Independent Safety Assessor covers design documents thoroughly.
- Train engineers and contractors in relevant standards and peer review requirements.
References
- RAIB report on loss of safety-critical signalling data. gov.uk.
- Construction Dive summary of FIU pedestrian bridge collapse. constructiondive.com.
