William Haddon Jr developed his conceptual model, the Haddon matrix, more than two decades ago applying basic principles of public health to the problem of traffic safety.1 ,2 Since that time, the matrix has been used as a tool to assist in developing ideas for preventing injuries of many types. As such, it provides a compelling framework for understanding the origins of injury problems and for identifying multiple countermeasures to address those problems. However, users then must decide for themselves among the alternatives. This paper adds a third dimension to the matrix to facilitate its use for making decisions about which countermeasures to apply.

Haddon's matrix

The matrix of four columns and three rows combines public health concepts of host-agent-environment as targets of change with the concepts of primary, secondary, and tertiary prevention.3 ,4 More specifically, the factors defined by the columns in the matrix refer to the interacting factors that contribute to the injury process (see tables 1 and 2). The host column refers to the person at risk of injury. The agent of injury is energy (for example mechanical, thermal, electrical) that is transmitted to the host through a vehicle (inanimate object) or vector (person or other animal). Physical environments include all the characteristics of the setting in which the injury event takes place (for example a roadway, building, playground, or sports arena). Social and legal norms and practices in the culture are referred to as the social environment. Examples include norms about child discipline or alcohol consumption or policies about licensing drivers or sales of firearms.

The phases in Haddon's initial configuration referred to rows in the matrix. These …