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The Haddon Matrix

Developed by William Haddon in 1970, his "phase-factor matrix" was developed to facilitate an assessment of the many things that contribute to injury occurrence and severity. Using this framework, one can then evaluate the relative importance of contributing factors and use that assessment to design prevention strategies.

Injury Definition

The term injury may be defined as damage to the body caused by exposure to environmental energy (kinetic, thermal, chemical, electrical, or radiation) in amounts that exceed the human body’s resilience. In epidemiological terms, the agent of injury is exposure to energy from an external source. However, poisoning, drowning, suffocation and exposure to extremes of ambient temperature are also considered injuries because normal body functions can be interrupted by these external exposures. To fit this definition of injury, the exposure should be acute – occurring in a fraction of a second, or at most within a few hours. Damage from longer exposures, such as to low levels of hazardous chemicals or ionizing radiation is usually classified as a disease.

The physical laws relevant to the behavior of energy have been known for hundreds of years. The laws of physics and knowledge of physiology, anatomy, and biomechanics may be used to predict the occurrence and severity of damage due to energy exposures.

Example: The Haddon Matrix For Motor Vehicle Occupant Safety

Factors →

Phases ↓
Personal Factors Equipment Factors Physical
Environmental Factors
Environmental Factors
Pre-event Driver skills

Driver attentiveness

Maintenance of brakes, tires, etc.

Windshield cleanliness
Roadway condition

Darkness or glare
Attitudes to drink driving and speeding,

Use of restraints
Event Human tolerances to crash forces

Wearing of seatbelts
Vehicle crashworthiness

Energy absorbing design

Presence of fixed objects near roadway

Unsecured objects within the vehicle
Enforcement of mandatory seatbelt and child restraint use
Post-event Crash victims general health status Petrol tanks designed to minimize likelihood of post-crash fire Availability of effective emergency response Public support for trauma care and rehabilitation

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