Human Factors in Accident and Incident Investigation and Reporting: A Framework for Understanding Human and System Errors in UK Railway Operations

Abstract: The Office of Rail and Road (ORR) describe a signal passed at danger (SPAD) as an event that occurs when a train passes a stop signal when not allowed to do so (ORR, 2023). Over the past 100 years there have been several significant SPAD accidents including Harrow and Wealdstone (1952), Southall (1997) and Ladbroke Grove (1999). The driver of the train involved in the SPAD at Purley in 1989 was prosecuted as they were blamed for the event. Years later the driver was acquitted after new evidence showed that there had been 4 previous SPADs at that signal so there was something about the design of the infrastructure that made errors more likely (RSSB, 2018). This highlights that the human and system failures need to be understood to effectively manage SPAD risk. Harrison et al., 2022 compared data on how many SPADs occurred on the mainline network per year with data on red aspect approaches (RAATs) (RSSB, 2023) to show that train drivers have a SPAD event on average 1 in every 43,000 red aspect approaches. When compared to the human error probability for this task in the rail action reliability assessment tool (RARA) (RSSB, 2019), it showed that train drivers are performing close to the limit of human performance. System improvements will therefore be key in reducing the number and risk of SPADs.The number of SPADs each year and the risk from SPAD events decreased following the introduction of train protection warning system (TPWS) but has now plateaued at 250-300 events per year. According to the Safety Risk Model (RSSB, 2022), SPADs account for a low percentage of overall risk on the railway (RSSB, 2022), however there is still the potential for catastrophic harm where trains pass a signal at danger and reach a point where conflict with another train is likely.A framework has been introduced into the GB rail industry's safety management intelligence system (SMIS) to understand the causes of signal passed at danger (SPAD) events. This paper will:•Introduce RSSB’s human factors framework including the recent addition of categories to better understand and report incidents where distraction is a factor•Provide analysis of SPAD incident data over the past 3 years•Describe how the framework has been applied to drive safety improvements within the RSSB rail health and safety strategy (RHSS) industry groups such as the train accident risk group (TARG), rail investigation group (RIG) and the infrastructure safety leadership group (ISLG) with regard to high risk SPADs, improving rail investigation and response, and engineering works•Discuss the future of SMIS in terms of work carried out to support the integration of AI in the investigation and reporting process•Evaluate the next steps applying the framework to understanding how system and human error contributes to other railway operating incidents such as train overspeed and trespass across the GB rail network, in addition to describing the support provided in applying the framework through the revision of the rail industry standard RIS-3119-TOM: accident and incident investigation.

Keywords: Accident and incident investigation and reporting, system failures, human performance, rail, safety, signal passed at danger, railway operations

DOI: 10.54941/ahfe1006537

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