When Software Goes Wrong - A City Metro System

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This podcast looks at the causes of an accident that happened on a city metro system while testing a new signalling system.

In this fifth podcast about the impact of software failures on railway asset safety, I talk with Dr Emma Taylor about the causes behind an accident that happened during testing on a city metro system. In this episode we highlight some of the failures as they relate to the stages in the V-model that is, or should be, applied to the software development lifecycle. A set of processes that is particularly important for verification and validation during the development, testing and implementation of complex software-based systems.  This is not a definitive assessment of the incident, just an analysis to increase understanding of complex software-based systems and their implementation.

One of the aims of this podcast is to share learning with the wider industry to support a wide range of stakeholders including train manufacturers and owners.

Listen to the podcast

Topics in this episode include:

  • Emma describes the importance of using the V-model to verify and validate the integrity of safety-critical software systems [2:04]
  • Emma describes the signalling failure incident and the major changes that were being tested [3:10]
  • Emma talks about the system definition step in the V-model, and her opinion of some assumptions made about the dependability of the core software [4:43]
  • Emma explains latent software faults [5:16]
  • Emma talks about the need for risk assessment, identification of hazards, and the design of software systems to avoid the identified hazards [5:50]
  • Emma gives some personal thoughts as to why a data synchronization issue might have been missed [7:25]
  • Emma talks about the practical stages of software development, the 'apportionment of system requirements' and the importance of recording changes in design [8:15]
  • Emma talks about the failure of data copying between systems and the related process documentation [9:20]
  • Emma talks about the testing part of manufacture, the verification and validation, throughout the lifecycle [10:22]
  • Emma describes the role of third-party, independent assessors in the development process [11:38]
  • Close [14:36]

Resources mentioned in this episode:

Other related resources:

RSSB podcasts cover a range of topics to keep you informed about things that will lead us all toward a better, safer railway. 'All our podcasts can be accessed from our podcast page.

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