In a review of 30 published health impact assessments on the costs and benefits associated with walking and cycling for transportation, substantial health benefits were found with a shift to active transportation. These benefits outweighed the negative effect of traffic incidents and air pollution exposure.
Mueller, Natalie, David Rojas-Rueda, Tom Cole-Hunter, Audrey de Nazelle, Evi Dons, Regine Gerike, Thomas Götschi, Luc Int Panis, Sonja Kahlmeier, and Mark Nieuwenhuijsen. (2015). Health impact assessment of active transportation: a systematic review. Preventive medicine, 76, 103-114.