Injuries

Drawing on the same social-ecologic principles that help describe the factors affecting the occurrence of injuries, William Haddon developed two frameworks for conceptualizing injury interventions. The first outlined injury interventions aimed at different phases in the energy transfer process. The ten countermeasures were directed at reducing the potential for damage to the body from an energy source. Table 5 shows examples pertaining to reducing childhood bicycle crash injuries.

Later, Haddon proposed a different, but similar, model to help stimulate intervention development: the Haddon Matrix. This model is widely used to identify potential interventions, and has two dimensions. The first depicts the target of change, including the person at risk (or the person's caretaker); the source of energy (e.g., products to which children are exposed—toys, motor vehicles, household poisons); the physical environment (e.g., playgrounds, roadways, homes, schools, day-care facilities); or the social environment (e.g., norms about behaviors such as drinking or child discipline; regulatory policies governing drinking ages, playground safety, or use of bicycle helmets). The second dimension depicts the phase at which the intervention has its effect— whether at the time of the injury event (e.g., a seat belt that deploys during a crash); at a time prior to the event, helping to prevent the event (e.g., antilock brakes); or after the event to reduce the effects of the event (e.g., gas tanks engineered to prevent explosions). Putting these two dimensions together creates a four by three matrix. Using the matrix as a brainstorming tool, one can fill in the twelve cells with ideas of potential interventions (see example in Table 5 pertaining to bicycle safety).

Choosing among the multiple alternative intervention ideas can be complex but several principles can help sort out the types of intervention ideas. Interventions may be voluntary or mandatory. And they might be active or passive. Active interventions require that the person to be protected takes protective action (e.g., putting on a bike helmet, testing water temperature in the baby's bathtub). In contrast, passive interventions are those that do not require action on the part of the individual being protected or deliberate action by a caretaker. Rather, they are engineered or set up such that protection is automatic (e.g., installation of airbags in cars, setting the temperature for hot water heaters at a safe level; automatic shutoffs on appliances). In general, interventions that require less individual effort result in more success. That is, passive interventions tend to be more successful than ones that require individual action. There are significant trade-offs, however, in making choices among the different options.

A third dimension added to the Haddon Matrix by Carol Runyan addresses the kinds of trade-offs that frequently occur in public health decision making. By considering alternative interventions derived from the two-dimensional matrix, a planner can examine the value issues involved in each choice and compare various options. As a result, decisions can be made more logically and the rationale for a given decision can be explained to others. For example, an intervention requiring restrictions on the purchase of firearms limits the freedom of gun enthusiasts, while at the same time affording greater freedom for children to live in environments with fewer guns and thus increasing child safety. Likewise, some interventions are more costly than others, requiring design changes in products (e.g., improvements in car design to reduce rollovers in crashes) or in the design of physical space (e.g., changing the equipment on a playground at a child-care facility). Other strategies require that funds be made available to make special provisions for protecting children without personal resources (e.g., car seat or smoke detector give-away programs for low-income families), while limiting higher-income families' access to the funds.