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C. The Haddon Matrix

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The Haddon Matrix is commonly used to approach safety analysis at a site in a systematic fashion.  Developed in 1980 by William Haddon, the Matrix is a two-dimensional model which applies basic principles of public health to motor vehicle-related injuries.  The first dimension is the phase of injury divided into pre-crash, crash, and post-crash.  The second dimension is the four factors of injury:  human, vehicle/equipment, physical environment, and socioeconomic.

The Haddon Matrix is completed through the evaluation of sites and/or crash details associated with a site or sites.  When completed, it provides insight into the range of possible safety issues and concerns as well as possible solutions.  This model is an extremely effective tool for not only identifying where and when to implement traffic safety countermeasures, but also planning crash-related data collection, and identifying organizations and agencies for collaboration efforts.

The value of the Haddon Matrix is each cell represents a different area in which interventions can be identified and implemented for transportation system safety improvement.  The Haddon Matrix is completed upon examination of crashes for a set of locations or single location under study, and is used to inform the road safety analyst.

For example, the Haddon Matrix below might be constructed from a set of crashes in an urban area.  The top-left cell (pre-crash human) identifies potential modifications to driver behavior that may reduce the likelihood or the severity of a collision.  As shown in the example table, it is poor vision or reaction time, alcohol consumption, speeding, and risk taking.  The matrix in its entirety provides a range of potential issues that can be addressed through a variety of countermeasures, including education, enforcement, engineering, and emergency response solutions (the 4Es of Safety).

Table C.1 Haddon Matrix

Not Applicable



Physical Environment



Poor vision or reaction time, alcohol, speeding, risk taking

Failed brakes, missing lights, lack of warning systems

Narrow shoulders,
ill-timed signals

Cultural norms permitting speeding, red light running, DUI


Failure to use occupant restraints

Malfunctioning safety belts, poorly engineered air bags

Poorly designed guardrails

Lack of vehicle design regulations


High susceptibility, alcohol

Poorly designed fuel tanks

Poor emergency communication systems

Lack of support for EMS and trauma systems

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Page last modified on July 15, 2011
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