A study conducted by researchers from Arizona State University, University of Washington, and the University of Texas at Austin has unveiled the significant ways extreme heat alters human activity patterns and mobility choices in major U.S. cities. As urban centers worldwide grapple with rising temperatures, these findings offer crucial insights for policymakers, urban planners, and transportation experts seeking to create more resilient and equitable communities.
On extremely hot days, people are markedly more likely to stay indoors, reducing time spent on outdoor activities and non-essential travel. The study analyzed data from 11 major U.S. metropolitan areas, finding that trips for leisure, shopping, and socializing decrease significantly when temperatures soar. Those who do venture out tend to shift their travel to cooler times of the day, opting for early morning or late evening excursions to avoid midday heat.
Transportation choices also undergo a notable transformation during heat waves. While car use increases, trips made by walking, biking, and public transit drop dramatically. Public transit usage, in particular, plummets by nearly 50% on extreme heat days as individuals seek refuge in air-conditioned private vehicles. This shift presents significant challenges for cities aiming to promote sustainable transportation options, especially as climate extremes become more pronounced.
The study highlights that certain groups face disproportionate challenges during extreme heat events. Low-income individuals and those without access to cars are more likely to rely on walking or public transportation, leaving them exposed to dangerous temperatures. These same individuals often have the least flexibility in terms of when and where they work, necessitating travel even in oppressive heat.
While higher-income individuals reported making significantly fewer trips on extremely hot days, lower-income individuals and those without car access did not show appreciable drops in daily trip-making. This suggests that they are more vulnerable and exposed to the deleterious effects of extreme heat. Older adults also experience greater challenges in adapting their daily routines and risk social isolation when sheltering indoors from the heat.
In light of these findings, the researchers propose a range of policy recommendations to help mitigate the impacts of extreme heat on communities. These include creating shaded public spaces, offering vouchers for on-demand door-to-door transportation for vulnerable populations, and declaring "heat days" when people are encouraged to stay indoors and access cooling centers if needed.
Urban design improvements, such as planting more trees and using heat-reflective materials on pavements, can also help make cities more resilient to rising temperatures. The study underscores the critical need for cities to incorporate heat mitigation strategies into their transportation and urban planning efforts, ensuring that all residents are protected from the dangers of extreme heat.
As extreme heat events become more frequent and severe, these findings provide timely and actionable insights for creating more heat-resilient cities. By addressing the challenges associated with extreme heat through thoughtful urban design and policy interventions, cities can work towards ensuring equity, public health, and well-being for all residents in an increasingly warm world.
