Societal Goals

Advancing Public Health

Transportation benefits public health in many ways. It brings the food and other services that people depend on to them and provides access to health care, family, friends, education, worship, and other societal amenities. Transportation can also harm public health, including through crashes, vehicle emissions, noise, and reduced physical activity levels.

By far the most harmful effects result from emissions of fine particulate matter 2.5 microns in size or smaller (PM_2.5).⁷⁸ After inhaling PM_2.5, the particles can enter the lungs, reach the bloodstream, and cause premature death or injury from heart or lung disease, aggravated asthma, irregular heartbeat, and difficulty breathing.⁷⁹ As many as 85,000 to 200,000 premature deaths in the United States annually are attributable to PM_2.5 from transportation and all other sources.⁸⁰

Motor vehicle emissions combine with other sources of atmospheric pollutants and natural sources of dust and other matter to form PM_2.5. Ambient concentrations of PM_2.5 vary considerably across the country depending on wind, weather, local conditions, and nearby sources, but are typically highest in the most urbanized areas.⁸¹ Federal clean air standards have helped reduce concentrations of PM_2.5 in the United States by 37 percent over the last two decades (see Figure 12).⁸² Even with these reductions, about 20,000 premature deaths due to motor vehicle PM_2.5 emissions were estimated in 2017.⁸³ The number would be almost 2.5 times higher if the vehicle emission rates of 2008 had persisted. Nonetheless, the annual level of estimated deaths attributable to PM_2.5 emissions increases by half the total from motor vehicle crashes. Roughly two-thirds of these premature deaths resulted from LDV emissions, primarily in urbanized areas. These rates highlight the importance of transitioning the motor vehicle fleet to electric power from renewable sources and reducing VMT by internal combustion vehicles (see the Climate Change section of this publication). Decarbonizing the fleet, however, will not eliminate health risks from transportation emissions. Tires release particulates and chemicals as they are used, which can contribute to respiratory and other ailments.⁸⁴ Engines dependent on fossil fuels, as well as low-carbon fuels, emit nitrogen oxides which can cause or exacerbate lung diseases, in addition to reacting with other atmospheric chemicals to form PM_2.5.⁸⁵

Poor air quality and the presence of particulates are not the only negative influences on health that arise from transportation. Noise, which is becoming increasingly common in urban areas, has negative effects on both physical and mental health.^86,87,88 Considerable effort has been made over the years to measure, monitor, and address noise impacts

around airports, but, aside from sound walls along urban Interstates, comparatively little effort has been made to reduce noise near major highways, railroads, freight depots, and ports.

Beyond the pollutants that transportation services generate, lack of transportation is also often a barrier to accessing health care, which negatively affects both individual and population-level health outcomes.⁸⁹ Transportation barriers can lead to missed appointments and delayed care, resulting in poorer long-term health outcomes, especially for chronic conditions. These barriers are especially pronounced for low-income and un- or under-insured individuals.

While there are many ways transportation affects public health negatively, certain forms of transportation can also generate positive health effects. Although the physiological mechanisms for improved health are not well understood, active travel, such as walking and cycling, is associated with important public health benefits,⁹⁰ including reduced cardiovascular

disease mortality,⁹¹ reduced risk of breast⁹² and colon cancer,⁹³ and reduced risk of type 2 diabetes.⁹⁴ However, it is not clear how to most cost-effectively encourage more people to choose active travel when it is available. Development patterns in most of the United States do not lend themselves to comfortable or convenient active transportation connections, as discussed in the Land Use section of this publication, and relatively few options dedicated to active travel exist. As jurisdictions support increasing options for walking and cycling, including on e-bikes, they need greater data-driven guidance on the design, location, and connectivity of sidewalks, paths, and bike lanes that are safe, convenient, and likely to stimulate sufficient active travel to cover their costs, especially where adding such facilities must be retrofitted into a busy built environment where land acquistion and infrastructure redesign costs are very high.

None of these public health effects, whether positive or negative, are evenly spread throughout the population. Low-income communities of color are disproportionately exposed to transportation emissions, noise, and traffic crashes, and disproportionately suffer adverse health and other consequences due to these exposures.^95,96,97 PM_2.5 from human activities, including motor vehicle emissions, also disproportionately harm people of color compared to their White peers,^98,99 in part because people of color are more likely to live close to busy roads and highways.¹⁰⁰ Both the costs and benefits of active transportation are inequitably distributed, with people of color experiencing more costs, including higher incidences of crashes when walking, and fewer benefits.¹⁰¹

Beyond the existing issues and disparities, the COVID-19 pandemic interacted with transportation and public health in multiple, complex ways. Transportation serves as a disease vector, and the industry struggled to understand how to minimize that role. The COVID-19 pandemic also caused disruptions in access to health care, transit access for essential workers, supply chains for personal protective equipment and medications, substitution of telehealth for in-person care, shifts from shared to solo vehicles, among other disruptions. Documentation of the effects of these myriad disruptions and development of lessons learned in adapting to COVID-19 would be invaluable for combating both the lingering effects of the recent pandemic and impacts of future events.

Reduced transportation emissions due to clean air regulation have improved public health. Even so, tens of thousands die prematurely from these emissions annually. Emissions will fall further as the fleet electrifies, but continued dependence on fossil fuels during the decades of transition to decarbonization ahead, as well as future reliance on alternative fuels with harmful emissions, will continue to harm populations exposed. Adverse impacts from transportation