Theories on Common Causes of Accidents
This is a short paper looking at what some theorists (Heinrich, Reason and Perrow) say about how accidents are caused.

Perhaps the most influential theory of accident causation has been Heinrich's Domino Theory of the 1920s. Essentially, the theory states that and accident leading to injury or damage is the result of a five stage sequence. Each domino therefore represents a linked cause. Remove any one of them and the sequence cannot run its course, and therefore damage or injury will not be incurred.

Over time, consensus has built up about the types of cause represented by each domino stage. By now, we know enough about the last two stages (the accident and resulting injury or damage), but some typical examples of the first three causes are:

There has also been development over time in the application of the model:

•  Prevailing initial interpretations saw the worker as the prime source of accidents, and concentrated on removing the third domino through a combination of disciplinary and protective measures.
• As MacGregor's Theory X and Theory Y of management gained influence, the emphasis switched to the second domino, and the preventive action centred more on training and work design
• More recently, safety theory and practice has focussed on the first domino, as belief has grown in the ultimate responsibility of senior management for safety matters, and in the importance of designing systems and processes which are safe from the beginning. 

The trend for leading organizations to integrate health and safety into mainstream management, has sparked a search for new accident causation models which recognize that organizational and workplace factors are at the root of most unsafe acts. One such model has been put forward by James Reason (2000).

The organizational factors in Reason's model include resource allocation, health and safety goals, delegation of responsibility and authority, workplace design, procurement of equipment, etc. These are communicated throughout the organization as workplace factors, such as policies and procedures, work schedules, instructions, training, and so on. These factors affect the frontline worker and (in accident scenarios) may influence them to cut corners for instance, to meet an urgent deadline, or to assume that a key maintenance action can be left for someone else to carry out.

Reason's model may be less attractive to the health and safety practitioner than Heinrich's because it offers less choice about where to begin tackling safety in the organization, and because the starting point it offers (organizational strategy and culture) may not be easy for the health and safety practitioner to influence. Even more discouraging is the belief among some experts, that the causation of accidents in certain high-risk systems, is too complex even to address from the standpoint of organizational factors. As Perrow (1999) says:

"[they] should be abandoned because the inevitable risks outweigh any reasonable benefits."

Nuclear power and weapons are most often cited, but often mentioned too are DNA technology and space travel.