Glossary of Data Variables for Fatal and accident causation ... - ERSO

Manual For SafetyNet accident causation system (SNACS)
km/h. From this you can say that the speed is more than adequate (given the
speed limits), but the stretch of road with an unblocked view of oncoming traffic
is too short. The latter part would indicate that the distance available for the
overtake is too short, making Distance a suitable genotype. However, a part of
normal driver education is to teach the driver not to overtake unless there is a
sufficient stretch of road with a free view, and hill crests are particularly
inadequate for overtaking. Given this, the phenotype that best describes the
situation would be Timing: premature action. The overtaking should have been
performed later on at a more appropriate stretch of road.
In practice, this does not have to be a very complicated problem, since the
linking table is constructed in such a way that phenotypes which are close also
have quite similar linking from the genotypes. This means that the choice of
phenotype does not have to be perfect, you can still get to the causes you need
for the analysis.
6.5.4 Subjective judgement
As the above reasoning shows, the SNACS methodology clearly calls for the
investigator to reason from a “normative” standpoint, i.e. the investigator has to
have an opinion on what would be normal or reasonable behaviour for a drivervehicle
system in the situation at hand, because otherwise it will be difficult to
classify what the deviation from the norm is. Also, the reasoning shows that the
choice of phenotype will be partially based on the investigator’s judgement. In
both these regards, a SNACS analysis will very clearly always be “subjective” in
some sense of the word.
This can be considered both an advantage and a disadvantage. People who
consider it a disadvantage will say that for a SNACS analysis we can never be
sure that two investigators will perform the analysis in the same way, since
subjective judgment is involved. This would be quite devastating for the
methodology, were it not for the fact that all methodologies which analyse
causes suffer from the same problem. As David Hume elegantly showed in his
treatise on human reason, causes typically cannot be observed; they have to be
inferred by reasoning. This means subjective judgement will always be involved
when analysing causes, no matter whether you are investigating injury
causation mechanisms in passive safety or accident contributing factors in
active safety.
In light of this, we find it preferable to have a methodology which transparently
shows that human judgement is involved, instead of burying that fact under
protocols designed to look “objective”. As for the problem of different
investigators performing different analysis, the best we can do is to clearly write
down the reasons we have for making our choices and then discuss these
reasons within the larger group of both your own accident investigation team
and several different teams meeting for case review. As has been pointed out in
the philosophy of science many times; over time a consensus within a larger
group or community is as close to the truth as any methodology analysing
causes will ever be.
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