The HEAT tool is designed to enable users without expertise in impact assessment to conduct economic assessments of the health impacts of walking or cycling. The tool is based on the best available evidence and transparent assumptions. It is intended to be simple to use by a wide variety of professionals at both national and local levels. These include primarily transport planners, traffic engineers and special interest groups working on transport, walking, cycling or the environment. The HEAT estimates the value of reduced mortality that results from specified amounts of walking or cycling, answering the following question: If x people regularly walk or cycle an amount of y, what is the economic value of the health benefits that occur as a result of the reduction in mortality due to their physical activity? In addition, HEAT can now also take into account the health effects from road crashes and air pollution, and effects on carbon emissions.