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)

An accident is a chain of five "dominoes"; the injury occurs only if the whole chain falls, and removing any one stops it:

1. Ancestry / social environment — traits/attitudes shaped by heredity and environment.
2. Fault of the person — carelessness, poor training, undesirable traits.
3. Unsafe act and/or unsafe condition — the central, controllable domino.
4. Accident — the event.
5. Injury / loss — the outcome.

Removing the third domino (unsafe act/condition)—via guarding, training, supervision—breaks the chain.

(ii) The Four M's (diagram)

      MAN (human)              MACHINE (equipment)
      - error, fatigue         - design, guarding, defects
             \                        /
              +------> ACCIDENT <----+
             /                        \
   MEDIA (environment)          MANAGEMENT (system)
   - workplace, noise           - policy, training, supervision

• Man, Machine, Media, Management—accidents arise from interactions among these; a failure/mismatch in any one, especially combined, produces the accident. Control any/all to prevent it.

(iii) Single-Factor Theory and Its Limitation

• Single-factor theory — an accident has one primary cause; remove it and the accident is prevented.
• Limitation — real accidents result from multiple interacting factors; attributing one cause (often "operator error") over-simplifies, stops the investigation early, encourages blame over system improvement, and leaves other contributing hazards uncontrolled—so recurrence is likely.