Question 1 of 7: Accident Causation Theories

Question 1: Accident Causation Theories (20 marks: 6/7/7)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Elements of Domino Theory (Heinrich)

1. Ancestry and social environment.
2. Fault of the person.
3. Unsafe act and/or mechanical or physical hazard (unsafe condition).
4. Accident.
5. Injury/loss.

The five factors are arranged like a row of dominoes: each knocks over the next, so the injury is the end of a chain rather than an isolated event. Removing the third domino (the unsafe act/condition) interrupts the sequence and the injury does not occur—which is why Heinrich's theory directs prevention effort at the unsafe act/condition rather than at ancestry or blame.

(ii) The Four M's (diagram)

      MAN (human)              MACHINE (equipment)
             \                        /
              +------> ACCIDENT <----+
             /                        \
   MEDIA (environment)          MANAGEMENT (system)

Man, Machine, Media, Management—accidents arise from interactions among these; control any/all to prevent the accident.

(iii) Single-Factor Theory and Its Limitation

• Holds an accident has one primary cause. Limitation: real accidents result from multiple interacting factors; single-cause thinking over-simplifies, stops the investigation early, encourages blame over system improvement, and leaves other contributing hazards uncontrolled (recurrence likely).