Application of Human Factors Analysis and Classification System (HFACS) to UK rail safety of the line incidents

Another study exploring rail safety events using HFACS. This evaluated 78 reports across 5 different types of incident.

All the usual caveats and limitations exist with evaluating and categorising incident reports. It does provide interesting insights on how rail investigators think about performance and contributing factors, though.

The HFACS model is shown below:

Results

Some key findings were that:

·????????Rail investigations had a strong focus on active failures and particularly those associated with work-related distraction and environmental factors

·????????Resultingly, “Few latent factors were presented in the reports” (p122)

·????????Results strongly suggest “the importance of a new factor – operational environment – that captures unexpected and non-routine operating conditions which have a risk of distracting the driver” (p122, new in the context of HFACS rather than new as in being previously unknown)

·????????The results highlight the need for rail to look more deeply at latent factors at the supervisory and organisational levels, rather than just on active factors related to people

Attentional factors were common (linked with 57% of events), like failing to notice the status of signals or distraction. 42% of factors associated with skill-based performance variability involved memory, like forgetting a station stop.

Decision errors were implicated in 12% of reports and included things like not stopping due to weather.

Procedural departures were linked in just 4% of reports. 2 were routine, with one involving drivers always stopping in an incorrect path of a platform to avoid passengers walking in the rain [** context and local rationality matters].

Adverse mental state was implicated as a pre-condition in 85% of events – e.g. fatigue, distraction, concentration etc.

The operating environment was implicated in 24% of events and technological environment in 18%.

Unlike aviation, crew resource management wasn’t a predominant contributing factor associated in these rail events – being listed in 8% of events.

Adverse mental state category had the lowest inter-rater reliability between the researchers coding the investigation reports (i.e. they disagreed the most on how to categorise this section).

Work-related distraction emerged the most, which was cited by drivers to be related to thinking about other work-related factors like the working environment, time pressures, driving patterns and the like.

Non-work-related distraction also occurred when the driver was thinking about things like relationship problems.

Drivers were significantly more likely to be distracted by work-related factors than than non-work-related [** although for obvious reasons this data is highly uncertain and non-verifiable.]

In 58% of distraction cases, the operating environment was associated as a strong contributing factor.

Supervisory and organisational factors were only identified in ~11% of investigations. Failure to correct a problem was the most common supervisory problem (8% of cases). Organisational process was the most common organisational factor (5% of cases); usually resulting from poor practices or procedures.

In discussing the findings, the authors argue that “the pattern of contributory factors for minor incidents is similar to that identified in more serious incidents … at least in terms of the Level 1 and Level 2 contributory factors [of the HFACS]” (p128).

Based on this secondary analysis, the authors note that “very few violations occurred … This suggests that minor incidents are more likely to be caused by an error or mistake than by a deliberate breach of rules” (p128).

Moreover, the role of the operating environment was strongly linked to work-related distraction and performance variability, such that weather, technical issues (faulty equipment), resulted in altered driving behaviour due to late running of trains and the like.

Further they discuss that “Cognitively, changes to the operational environment create a situation where the driver moves from a skill-based, proactive feedforward mode of control (Rasmussen, 1983; Hollnagel and Woods, 2005), to a more rule-based, and cognitively effortful (and error prone), reactive mode of control. To amplify the risk, this change of mode takes place just at that point where the driver is likely to be late or trying to preserve tight performance allowances in the timetable. Thus, they have the paradox of needing to work faster at a time when the environment demands, cognitively, that they take longer” (p129).

Finally they discuss issues with the quality and depth of investigations. Many failed to dive into supervisory and organisational levels of analysis. Thus, there was a rather large description of active performance of frontline operators, but little regarding the organisational and situational context [** and based on the paper, virtually nothing about design was mentioned].

Link in comments.

Authors: Madigan, R., Golightly, D., & Madders, R. (2016). Accident Analysis & Prevention, 97, 122-131.