Causes appear to be difficult things and causation appears to be a difficult subject. A brief check of safety books in the shelf over my desk shows astonishing variations. Heinrich decides to focus on direct causes, Hendrick & Berner completely reject the notion in their 1985 book “Investigating Accidents With STEP” and Hollnagel appears to reject root causes (see his great 2004 book “Barriers And Accident Prevention”). All explain things differently and have their reasons: Hendrick and Berner choose to equate cause to blame, Hollnagel not as much rejects root causes altogether but the notion of the root cause and application to intractable systems (see pages 105 and 106 of his ETTO book) and for Heinrich I’d like to point to my earlier discussion of his work.
As if this isn’t enough safety literature is littered with an incredible number of terms: direct causes, basic causes, underlying causes, root causes, proximate causes, latent conditions, unsafe acts, contributing factors, causal factors, and what not. While there seems to be some kind of general acceptance and understanding of those, one quite often comes across differing interpretations and then flaming discussions are adding to the confusion.
Something that gets me rather confused are ‘proximate causes’. This may be partly due to my ignorance (and the fact that this term is not used in the Dutch language when you study safety or law). Heinrich defined these as “unsafe personal act or unsafe mechanical hazard that results directly in an accident”. Heinrich’s definition is for me clearly a definition of ‘direct causes’. This is agreed upon by that most scientific of all sources, Wikipedia: “In philosophy a proximate cause is an event which is closest to, or immediately responsible for causing, some observed result”. Equating proximate and root causes (as I saw not too long ago) is a concept that I find difficult from a contemporary safety science point of view and in my opinion not very helpful for safety work either.
Conditions and causes
Many safety professionals appear not to be aware of the difference between causes and conditions (you may call the latter context as well, if you want), which sometimes ends up in quite strange causation, all too often blending in context. As an illustration: a few years ago I was one of the people responsible for cleaning up the ‘taxonomy’ of causes in our incident registration/management system. The status at that moment was one of unguarded organic growth over 15 years. Originally the off-the-shelf version had contained Bird’s sequence as the three main categories: Management Failures, Basic Causes (with sub categories for Personal Factors and Job/Environmental Factors) and Direct Causes. Into this structure there had been added elements over the passing of years without any proper policy or philosophy. Often the new elements ended up in ‘wrong boxes’ (e.g. ‘planning’ as a direct cause) and there were exceptionally many context items (e.g. ‘performing work in the rail tracks’) mixed in. Sure, absence of these things would have ‘prevented’ an accident from happening, but it would also have prevented accomplishing the intended outcome. So there is a lesson here, since I do not consider the people who worked with this system in the 15 years before me as complete idiots (something I’m not even qualified to diagnose anyway).
Among professionals there has been the debate if and how an (unsafe) condition can be a cause. I’m in the camp of people who think some conditions can be causes, but not always and automatically. Hart and Honore posed that “causes are what made the difference, mere conditions on the other hand are just those [things] that are present alike both in the case where accidents occur and in the normal case where they do not; and it is this consideration that leads us to reject them as the cause of the accident, even though it is true that without them the accident would not have occurred…”. I find this a rather useful and clarifying definition. Let’s apply it to some examples:
If someone bumps into a lamp post out on the street I agree that we’re talking about the lamp post as a mere condition. Sure, had it not been there, no one would have bumped in it. But reasoning in the line of “what would have prevented the accident from happening” and labeling those things causes is counterfactual reasoning and a fallacy without establishing a proper causal relationship first. The lamp post is intended to be there, was built in accordance with relevant standards and it stands there in the normal case of people not bumping into it and is just minding its business of lamp-posting.
If a workshop burns down after a discarded match sets discarded scraps of paper on fire, I do not agree with the view that only the match was the cause of the fire and the scraps of paper a mere condition. This based on the fact that I refuse to see scraps of paper thrown on the ground as being the normal case. If dumping your trash on the ground is acceptable (regarding it as an unwelcome but normal standing condition), then discarding a match is the same (after all people throw down matches and cigarette butts all the time, most of the time not causing fires). Even more since discarding a match on a concrete floor with no flammable material present would not have made the difference either. So in this example I see two things joining up as causes, namely the act of discarding the match and the condition-turning-cause of the scarps of paper lying there. Counting the last bit of the old-fashioned fire triangle (i.e. oxygen) as a cause, however, would be bullocks. Merely based on the ‘normal case’ argument… Absence of oxygen in this situation would hardly qualify as normal, would it?
Cause-effect relationships have to be explained with logic and must be based on facts (not hunches or guesses, not even on experience!). Anything written down in an investigation report must be able to stand up in a court of law, but hopefully never will. I find the “beyond a reasonable doubt” criterion a good one, and in the case that conclusions have to be based on assumptions/theories/hypotheses this must be clearly stated as such.
The example elsewhere on this blog hopes to illustrate the point about causes and conditions further. This example also shows another difficulty: it’s fully possible to write down acts as conditions and vice versa. The discarded newspaper isn’t quite as clear as the example where the condition ‘not wearing safety goggles’ essentially is the same as the act ‘does not put on safety goggles’.
By the way, a legal background may partly influence what to call a cause and what not because law can only handle people and thus will be focused on human acts. If there are any conditions identified the question usually will be who has caused them. In safety this appears to me as a not very useful notion. In my view cause in law is not quite the same as cause in safety and I find it not useful to define causes in a strict theoretical and legally sound manner. This will not really help preventive actions, but is probably great for judges and lawyers.
So, while I have learned to appreciate some of Hart and Honore’s work as very useful and clarifying (they have been added to my personal list of things-to-read-when-I-grow-up) I will look for causes in a safety context. Especially since the goals are different. Causes in safety must help to define actions while causes in law help other goals. In the newspaper example I can imagine that a judge rules a discarded match being an act of greater carelessness than discarding a newspaper. And I would agree, one reason I could imagine this being ‘more’ cause than the newspaper. Still, you need both and both are acts out of the ordinary that together ‘make the difference’, so in safety terms it’s useful to regard both as causes.
There’s another reason why I’m not particularly happy with thinking about causation in the legal sense: laws and even entire legal systems are quite different from one country to the other (just compare the UK to Germany or France) which may, or will, have consequences for the legal interpretation of or legal requirements for the term ‘cause’. In contrary the language of prevention in safety should be a common one that is understood by all safety professionals, regardless their countries of origin.
Conclusions (sort of)
Three things so far…
Causes in law and causes in safety are not necessarily the same thing. Beware of mixing them up.
The distinction between causes and conditions/context is an area that many safety professionals have too little awareness of. I’m sure that more focus and greater clarity on this will strengthen incident analysis and recommendations for preventive action.
It would be a good thing if the safety world would start to agree on what we call cause and what not, if necessary with some additional cause categories (direct, root, …). Or maybe we should stop using the word cause altogether and use another more neutral term? ‘Contributing factor’ has been proposed and Alan Quilley came up with “factors to be considered to prevent recurrence of the events that led to the unintended consequence”, but I believe FTBCTPROTETLTTUC is an impossible to sell acronym.
Feel free to comment and add more thoughts!