promoting public health; as indicated, lack of assessment can have many unexpected adverse health (and economic) consequences. One striking example is development of the transportation infrastructure in the United States. In 1956, Congress passed the Interstate Highway Act, which resulted in a transportation infrastructure focused on road-building and private automobile use and has shaped land-use patterns throughout the country. The emphasis on motorized transportation has been associated with more driving, less physical activity, higher rates of obesity, higher rates of air pollution, and transportation injuries and fatalities. A partial accounting of the costs of health outcomes wholly or partly associated with transportation indicates that the costs could be as great as $400 billion annually. No one can know how much the costs could have been reduced if health had been integrated into the decision-making. Without a systematic assessment, the health-related effects and their costs to individuals and society are hidden or invisible products of transportation-related decisions.

Several approaches, methods, or tools could be used to incorporate aspects of health into decision-making, but HIA holds particular promise because of its applicability to a broad array of policies, programs, plans, and projects; its consideration of adverse and beneficial health effects; its ability to consider and incorporate various types of evidence; and its engagement of communities and stakeholders in a deliberative process. The following sections define and describe the elements of HIA, the challenges to its practice, and the approaches to advancing it and integrating it into today’s decision-making processes.


On the basis of its review of HIA definitions, practice, published guidance, and peer-reviewed literature, the committee recommends the following technical definition of HIA, which is adapted from the definition of the International Association for Impact Assessment:

HIA is a systematic process that uses an array of data sources and analytic methods and considers input from stakeholders to determine the potential effects of a proposed policy, plan, program, or project on the health of a population and the distribution of those effects within the population. HIA provides recommendations on monitoring and managing those effects.

The committee emphasizes that HIA is conducted to inform a decision-making process and is intended to be concluded and communicated in advance of a decision so that the information that it yields can be used to shape a final proposal in such a way that adverse effects are minimized and beneficial ones are optimized. The committee acknowledges that other assessment methods may share some features with HIA, but they do not meet the definition and description of HIA that the committee provides in the present report.

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