The majority of collisions at railroad crossings are the result of:

Malfunctioning signals

Poor visibility

Faulty brakes

Human error

The answer is human error. It is because there are things that humans do, having them to lead to accidents or collisions. Such as when the person does not follow the rule of being cautious when crossing on the rail road, when the person ignores the rule of having to stop and checking both ways before passing through, when he or she does not see the incoming train in which she or he fails to see, he or she will likely lead to an accident.