2017 - Research

Health and greenhouse gas mitigation benefits of ambitious expansion of cycling, walking, and transit in California

Key takeaway:

  • By 2020, California aims to double walking and triple cycling from a 2010 baseline.
  • Proposed regional transportation plans with ambitious active transport targets are projected to significantly reduce the burden of disease and injury in California, based on the Integrated Transport and Health Impacts Model. However, increasing active transport will require spatial separation of motorized traffic and bike/pedestrian paths, speed reductions on local and arterial roads, and greater enforcement of dangerous driving.

Results:

  • In the United States, physical inactivity accounts for approximately six percent of all deaths; 30 percent each of heart disease, diabetes, colon cancer, and breast cancer; 13 percent of cerebrovascular disease; and 21 percent of Alzheimer’s disease.
  • The researchers modeled four alternative scenarios to a 2010 baseline that reflect ambitious growth in active transport and decline in automobile travel, while maintaining the total miles traveled across all modes. The alternative scenarios saw significant modal shares increases for cycling, walking, public transit, and a blend of the three. The cycling scenarios were projected to generate the most health and environmental benefits (in reducing statewide carbon emissions), compared to Walk and Public Transit scenarios. Although cycle scenarios generated a substantial increase in bicyclist injuries, they were to a much smaller extent than the increase in distance cycled.
  • The Walk scenario generated substantial health benefits despite increasing pedestrian fatalities, but was the least effective in reducing carbon levels since walking covers much shorter distances than bicycles or public transit.
  • The Public Transit scenario generated the least health benefits compared to cycling and walking.
  • The San Francisco Bay Area was the only region that demonstrated consistent reductions in carbon emissions in the Cycle, Transit, and Blend scenarios: It had a less polluting car fleet as well as the highest per capital baseline of active transport and transit, and a low per capita car vehicles miles traveled.
  • Spatial separation of motorized traffic and bike/pedestrian paths, speed reductions on local and arterial roads, and greater enforcement of dangerous driving are vital to catalyze a greater shift to active transport.
  • Including explicit carbon targets tied to levels of walking, bicycling, and public transit in regional and state plans may strengthen active transportation as a strategy for carbon mitigation.

Implications:

  • The finding that cycling scenarios were projected to generate the most health and environmental benefits, but also result in greater bicyclist injuries, underscores the need for quality and safe cycling infrastructure in order to optimize the health and environmental benefits of cycling.

Methods:

  • The researchers quantified health co-benefits and carbon reductions resulting from California regional transportation plans with ambitious levels of active transport by using the Integrated Transport and Health Impacts Model (ITHIM). The ITHIM used data from travel and health surveys, vital statistics, collision databases, and outputs from regional and statewide travel modes to estimate changes in the population disease burden resulting from a shift towards more active transport (i.e., walking and bicycling).

Maizlish, N.; Linesch, N.; Woodcock, J. (2017). Health and greenhouse gas mitigation benefits of ambitious expansion of cycling, walking, and transit in California. Journal of Transport & Health, 6.