• In this study, the authors sought to quantify benefits from reducing automobile usage for short urban and suburban trips.
• The authors simulated census-tract level changes in hourly pollutant concentrations from the elimination of automobile round trips ≤ 8 km in 11 metropolitan areas in the upper Midwestern United States using the Community Multiscale Air Quality (CMAQ) model. Next, they estimated annual changes in health outcomes and monetary costs expected from pollution changes using the U.S. Environmental Protection Agency Benefits Mapping Analysis Program (BenMAP). In addition, the authors used the World Health Organization Health Economic Assessment Tool (HEAT) to calculate benefits of increased physical activity if 50% of short trips were made by bicycle.
• The authors estimate that, by eliminating these short automobile trips, annual average urban PM_2.5would decline by 0.1 µg/m³ and that summer ozone (O₃) would increase slightly in cities but decline regionally, resulting in net health benefits of $4.94 billion/year [95% confidence interval (CI): $0.2 billion, $13.5 billion), with 25% of PM_2.5 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 1,295 deaths/year (95% CI: 912, 1,636) because of 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 billion, $5.0 billion]. They also estimate that the combined benefits of improved air quality and physical fitness would exceed $8 billion/year.
• The study findings suggest that significant health and economic benefits are possible if bicycling replaces short car trips. Less dependence on automobiles in urban areas would also improve health in downwind rural settings.

Grabow, M. L., S. N. Spak, et al. (2012). “Air Quality and Exercise-Related Health Benefits from Reduced Car Travel in the Midwestern United States.” Environmental Health Perspectives 120(1): 68.