Heinrich posits five metaphorical dominoes labeled with accident causes. They are Social Environment and Ancestry, Fault of Person, Unsafe Act or Mechanical or Physical Hazard (unsafe condition), Accident, and Injury. Heinrich defines each of these “dominoes” explicitly, and gives advice on minimizing or eliminating their presence in the sequence. Heinrich’s Domino Theory states that accidents result from a chain of sequential events, metaphorically like a line of dominoes falling over. When one of the dominoes falls, it triggers the next one and the next continuously. But removing a key factor (such as an unsafe condition or an unsafe act) prevents the start of the chain reaction.
Frank Bird (1970) developed Loss Control Theory. Suggested that underlying cause of accidents are lack of management controls and poor management decisions. Problem: not so popular & blames management (responsibility and control).
In 1980’s, Behavioural Based Safety (BBS) was introduced based on Heinrich’s findings. Work by recognizing safe work habits and offering rewards and punishment. Problem: focuses on workers and not on hazard or management & reward and punishment system have flaws.