5.5
Accident Investigation
Why investigate accidents, and who does this?
Why?
Who?
Distinction between law enforcement investigation and accident investigation
Accident investigations by safety agencies are not about assigning blame. Instead the aim is to enhance future safety.
Investigations for law enforcement, by the police or prosecuting bodies, seek to identify if law(s) have been broken.
The focus of an accident investigation is on:
How
Why
What
The findings of the accident investigation provide an opportunity to prevent future accidents by identifying lessons learned
In an organisation with a strong safety culture, which you learned about in the previous lesson, accident investigation findings are acted upon promptly and effectively, without this needing to be forced on the organisation by legal compulsion.
Companies conduct their own internal accident investigations.
there are many different agencies and specialist bodies that investigate accidents
US: Chemical Safety Board; National Transportation Safety Board
UK: Air Accidents Investigation Branch; Marine Accident Investigation Branch; Rail Accident Investigation Branch
Japan: Japan Transport Safety Board
Canada: Transportation Safety Board of Canada
International: International Atomic Energy Agency
Accident investigation process
Accident investigations require a systematic, detailed approach
Steps
Step 1: Information gathering:
debris field mapping
collection of samples from the accident site
interviews with witnesses
retrieval and interrogation of data recording devices.
Step 2: Analysis:
laboratory studies (e.g. of fracture surfaces), debris re-construction etc.
modelling and simulation (this depends on the nature of the accident)
root cause analysis (see below).
Step 3: Identification of the causes of the accident
Primary causes of the accident. These are what actually made the accident happen.
Contributory factors to the accident. These made the accident more likely and/or more severe than would otherwise have been the case.
Step 4: Make recommendations:
identify new control measures needed
identify an action plan for implementing these controls.
Root Cause Analysis
A useful tool to analyze accidents
Root cause analysis of an accident seeks to determine not just what happened but also how and why. It encompasses not just unsafe acts, local workplace factors and organisational factors.
Root cause analysis identifies:
Immediate causes: features of the accident that immediately contributed to the outcome (be this injury and/or property damage). These are what directly caused the accident and immediately contributed to harm.
Underlying causes: these items did not themselves cause harm, but made a significant contribution to the accident as indirect causes.
Root causes: These are aspects of safety management that failed and therefore allowed a climate to develop in which the accident occurred.
The causal path of the accident starts from the root cause(s) and goes to the ultimate outcome (the accident).
Fault Tree Analysis
provides a means of identifying the ‘anatomy’ of an accident using a Boolean approach (using, for example, ‘and’, ‘or’ and ‘not’).
provides a way of looking at an accident that is complementary to a root cause analysis.
Making Recommendations
To be effective each recommendation in an accident report should be SMART
Specific – the area for improvement should be defined clearly, for example
highly specific recommendations in response to the accident itself (often these will be in response to the immediate or underlying causes of the accident)
systemic recommendations to address broader issues revealed by the investigation (often these will be related to the root causes of the accident)
Assignable (Actionable) – the body or person that needs to act is defined.
Measurable – there are clear metrics of success and progress.
Realistic – even if some changes might not be practical, it’s better that the organisation achieves some safety improvement than none at all
Time-based – if not, action will be postponed for ‘later’. This could include
immediate recommendations e.g. narrowly targeted engineering or procedural fixes that can be delivered quickly
longer-term recommendations e.g. fundamental technological, process, or training redesign that require substantial changes.