Most serious, public transport accidents are investigated to a greater or lesser extent but,
with some conspicuous exceptions, particularly with aviation, only a few are done with the
aim of improving safety. Many have been investigated with the aim of apportioning blame or
liability and although safety recommendations are often made, they frequently fail to identify
some of the underlying causes of whatever went wrong.
An accident is rarely the result of a single event. More often, it is caused by a combination of
unrelated events coming together. In many modes, the human element in this causal chain
can be significant. When an accident occurs, it is normally the result of one or more
shortcomings in the safety system. People rarely make mistakes deliberately, but will often
do things that have serious consequences.