Health and Safety Executive Human Factors in Accident Investigation David Birkbeck HID Onshore Human & Organisational Factors Group

Health and Safety Executive Health and Safety Executive Human Factors in Accident Investigation David Birkbeck HID Onshore Human & Organisational Factors Group

Introduction To say accidents are due to human failing is like saying falls are due to gravity. It is true but it does not help us prevent them Trevor Kletz Aim today is to present methods that are known to help identify human failure in accident investigation and prevent reoccurrence Not a black art, a pragmatic and robust process

What we expect Methodical process for gathering information, analysing what went wrong (and right), and learning lessons in order to: –Manage risk –Prevent reoccurrence Retrospective tool, but can be powerful in promoting change

Accident reports What happened Who to When How it happened But not why Technical myopia Failure to consider human factors

Significance of human factors Up to 90% of accidents attributable to some degree to human failures...Texas City…Buncefield... …Texaco Milford Haven... Southall and Ladbroke Grove crashes...Zeebruger… Proportion and significance increasing as technical safety measures improve

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But not as simple as we think.. This accident was the result of human error –…..pilot error Error or rule-breaking put down to –Lack of competence –Poor supervision –Not paying attention Its not usually as simple as that!

Human failure taxonomy MistakesLapsesSlips When the person does what they meant to, but should have done something else When the person forgets to do something When the person does something, but not what they meant to do Human failures Unintended actionsIntended actions Errors - Unintended consequences When the person decided to act without complying with a known rule or procedure Violation - Intended consequences

Slip, lapse or mistake? Involuntary or non-intentional action Was there prior intention to act? Did the actions proceed as planned? Did the actions achieve their desired end? Successful action Was there intention in the action? Spontaneous or subsidiary action Unintentional action (slip or lapse) Intentional but mistaken action Yes No

How to apply Create timeline Identify significant behaviours Analyse behaviours Identify effective measures to prevent reoccurrence Record

Errors Slip –When a person does something, but not what they meant to do Lapse –When a person forgets to do something Both are unintended actions with unintended consequences

Example slip – Emirates EK407 Emirates Flight EK407 Pre-flight take off calculations were based on an incorrect take off weight (262M/t rather than 362M/t) This weight was entered into take off performance software on separate laptop Captain noticed something was wrong at the end of the runway, took manual control and selected maximum thrust

Example slip – Emirates EK407

After the accident, Captain and First Office were asked to resign by Emirates and did so ATSB investigation revealed: –Captain had flown 99 hours in last month (1 hour below maximum) –Had slept for 3.5 hours in 24 hour period prior to flight (shift rotas) –Excessively complex system for calculating take off speed (manual transfer of information from 2 automated systems) –No automated failsafe

Mistakes When a person does something they intended to do, but should have done something else Rule based – choosing a standard solution for a known problem – the maintenance worker who selects the wrong isolation procedures Knowledge based – working from first principles – 3 Mile Island shift team dismissed a potential explanation for the unfolding incident as they believed a valve was closed

Mistakes Because the action is intended, mistakes are much harder to detect at the individual level People believe what they are doing is right and often dismiss evidence to the contrary –Bias –Tunnel vision

Violations The Texas City technicians who filled the raffinate splitter to % capacity rather than 50% as stated in procedures The Assistant Boson who was asleep rather than checking the bow doors were closed on the Herald of Free Enterprise The technicians who knowingly maintained the Chernobyl reactor in an unsafe state to allow a safety study to be conducted

Violations Violation –When a person decides to act without complying with a known rule or procedure Note that, in this context, there must be an known rule or procedure This is not a moral or ethical judgement

Violations

Note that we all integrate rule violation into our day to day lives so the identification of a violation should not be regarded as a precursor to discipline Indeed, we tend to like those who break the rules

Violations

Types of violations –Routine –Exceptional –Acts of sabotage The key to the effective analysis of violations is to understand why –What antecedents were present? –What behaviour was observed? –What consequences resulted?

Performance Influencing Factors Defined as the characteristics of the job, the individual and the organization that influence behaviour Considered during behavioural analysis, often at the end of the process Very broad topic including a range of factors e.g. fatigue, group effects, design of equipment, mental wellbeing, task knowledge/complexity A comprehensive list available on HSE website Often have a critical role in error causation but equally often overlooked (e.g. fatigue EK407)

Performance Influencing Factors Can profoundly influence potential for error (proposed nominal human unreliability). Task is: Routine, highly practiced, rapid task involving relatively low level of skill (0.02)* Miscellaneous task for which no description can be found (0.03)* Fairly simple task performed rapidly or given scant attention (0.09)* Totally unfamiliar, performed at speed with no real idea of consequence (0.55)* *Williams, J.C. HEART Technique

Common issues Failure to correctly specify behaviour –The individual involved –The task they were engaged in at the time –What they did (or did not do) –What the outcome was Making early decisions and sticking to them –As information becomes available, a mistake can become a violation Failure to identify the multiple behaviours contributing to an accident or incident –Timeline critical

Why bother with any of it? Each failure type has a different set of solutions designed to prevent their reoccurrence. For example (not exhaustive): –Slip/Lapse NOT training Hardware solutions Cross checks PIFs –Error Training e.g. scenarios Group support Challenge –Violations Behaviour modification Culture improvement

What to remember Human behaviour can be predicted with reasonable accuracy Correctly integrating HF into your accident investigation process will reap rewards – just look at the contemporary causation figures Separating error, mistake and violation represents a highly valuable first step Help is out there –Guidance –HSE –Industry working groups e.g. Energy Institute

A final thought The most powerful influence on human behaviour is outcome Therefore managing human failure requires a high degree of corporate honesty: –What behaviour is really rewarded? –Are we willing to look at organizational factors, especially when we see rule breaking? – Are we willing to make the investments that are likely to prevent reoccurrence? –Are we willing to strive for objectivity and pragmatism?

Sources of guidance Reducing Error & Influencing Behaviour HSG 48 Investigating Incidents & Accidents HSG 245 Successful Health & Safety management HSG 65 Human Factors Website pages Energy Institute guidance