I don't want to be too insistent, but: if you get hit by lightning or a falling rock while cycling or driving along, that's no-ones fault. But as long as two vehicles are involved, there is a set of well-defined rules that are designed to make sure that these vehicles don't collide, and if they do collide, in the overwhelming majority of cases one (or both) of the parties involved has failed to follow these rules, i.e. negligence.