Background: Promoting walking and cycling as modes of transportation offers several benefits, such as reducing pollutant emissions and increasing physical activity among the population. However, at the same time, people who adopt these active modes of transportation may face an increased risk of traffic accidents and exposure to pollutants. The European research program TAPAS (2009–2013) was developed to help policymakers design urban policies that contribute to the fight against climate change and encourage health-promoting practices while reducing the potential risks associated with these practices. Methods: Quantitative health impact assessment (HIA) models were developed as part of a multidisciplinary approach to estimate the overall impacts, in six European cities, of policies promoting active transportation. This paper presents the HIAs conducted in Barcelona (Spain) regarding the impact of installing a bike-sharing system and the impact of scenarios involving a shift from car use to cycling and public transit. The impacts on mortality and morbidity, in terms of risks associated with increased exposure to pollutants and traffic accidents, as well as the impact of physical activity, were estimated. Results: Regardless of the scenario, the benefits associated with physical activity resulting from active transportation modes or from the shift to public transit outweigh the risks associated with increased exposure to air pollution and traffic accidents. A reduction in greenhouse gas emissions is also observed, for example, by 9,000 tons per year in the case of the implementation of the bike-sharing system in Barcelona. Conclusions: The health benefits to the population of urban policies aimed at promoting walking and cycling outweigh the risks associated with increased exposure to air pollution and traffic accidents. To fully assess these benefits, new health impact assessments are needed to identify the most effective policies for promoting active transportation and to determine the characteristics of the people most likely to adopt these modes of transportation, with the lowest possible environmental and individual risk.