• The authors simulated census-tract level changes in hourly pollutant concentrations from the elimination of automobile round trips ≤ 8 kilometers in 11 metropolitan areas in the Upper Midwestern U.S. using the Community Multiscale Air Quality (CMAQ) Model. Next, they estimated annual changes in health outcomes and monetary costs expected from pollution changes using EPA’s Benefits Mapping Analysis Program (BenMAP). Finally, they used WHO’s Health Economic Assessment Tool (HEAT) to calculate the benefits of increased physical activity if 50% of short trips were made by bicycle.
• The authors estimate that annual average urban PM2.5 would decline by 0.1 µg/m3 and that summer O3 would increase slightly in cities but decline regionally, resulting in net health benefits of $3.5 billion/year (95% CI: $0.4–$9.8 billion), with 25% of PM2.5 and most O3 benefits to populations outside metropolitan areas. Across the study region of approximately 31.3 million people and 37,000 total square miles, mortality would decline by approximately 1,100 deaths/year (95% CI: 856 – 1,346) due to improved air quality and increased exercise. Making 50% of short trips by bicycle would yield savings of approximately $3.8 billion/year from avoided mortality and reduced health care costs (95% CI: $2.7 – $5.0 billion). We estimate that the combined benefits of improved air quality and physical fitness would exceed $7 billion/year.
• Our findings suggest that significant health and economic benefits are possible if bicycling replaces short car trips. Less auto dependence in urban areas would also improve health in downwind rural settings.

Grabow, M. L., S. N. Spak, et al. (2011). "Air Quality and Exercise-Related Health Benefits from Reduced Car Travel in the Midwestern United States." Environmental Health Perspectives.