Plans crafted by metropolitan planning organizations (MPOs) lay out how billions of dollars in transportation investments will be made over a 20 to 30-year time horizon. Federal transportation authorizations require MPOs to identify and track key indicators of system performance (e.g. collision rates, emissions, congestion) to ensure that they are stewarding public funds wisely to meet specific goals related to safety, environmental performance, and congestion mitigation, among other areas. Concerns related to preventing discriminatory impacts of planning activities, motivated by Title VI of the 1964 Civil Rights Act, also compel agencies to assess the impacts of plans on different demographic groups. At the same time, there is a growing desire among transportation planning agencies to develop transportation and land use plans that shift travel behavior away from driving and towards more active travel modes. Research has shown that living in areas where walking and bicycling are convenient leads to greater use of those modes, which can lead to improved health outcomes due to increases in physical activity. But increasing non-motorized travel can also increase active travelers’ risk of traffic injury and exposure to air pollution. Analytical tools that assess the tradeoffs between transportation plan alternatives are needed to inform public debate and ensure that gains in some health outcomes are not being undermined by losses elsewhere. Additionally, questions remain about who will benefit from plans that promote increases in active travel. The aim of this project is to investigate the distribution of public health impacts resulting from a regional transportation plan in the six-county Sacramento Area Council of Governments (SACOG) region.

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Understanding the public health impacts of transportation plans can inform decision making and project prioritization. Because each plan and regional context is different, there is a need for site-specific methods to assess the extent and distribution of health impacts of changes to a region’s transportation system. To fill this need, researchers have developed the Integrated Transport and Health Impact Model (ITHIM), which predicts the public health impacts of transportation and land use scenarios from expected changes in air quality, traffic safety, and physical activity. However, current transportation health impact assessment models (including ITHIM) operate at coarse geographic scales (e.g., region or county) to quantify health changes. This research builds on previous work using ITHIM to generate demographically explicit health outcomes to provide neighborhood-level estimates of public health changes predicted from transportation plan scenarios in Sacramento, California.

We assess the impacts of regional transportation plan scenarios on public health via changes in traffic injury and physical activity. Zip-code level results are mapped using a customizable web interface. Illustrative results indicate that the adopted regional transportation plan will lead to improved health outcomes, largely driven by the benefits of increased physical activity. However, these estimates vary widely across the region, with some communities expected to experience adverse impacts and others obtaining higher levels of benefit. We note that some of the variation may be the result of modeling noise, and we identify promising avenues for improving the robustness of estimates at small spatial scales.

Disaggregation is important from sustainability and equity perspectives to determine the locations where and populations for whom the physical activity benefits of non-motorized transportation are outweighed by increased exposure to the risk of air pollution and injury or death. Providing an accessible, web-based tool to illustrate the effects of transportation plans and in communities across a region has the potential to elevate health and equity considerations in transportation decision making. The methods developed in this study can be refined and improved and applied elsewhere by modifying the source code, which is publicly available.

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