A recent study has shown that extreme heat has a considerable impact on people’s everyday activities, causing them to spend less time outdoors and change their transportation methods. Those most at risk include low-income individuals who lack access to vehicles, making it harder for them to evade hazardous conditions. The research emphasizes the need for specific policy actions, such as establishing shaded public areas, declaring “heat days,” and improving urban design to lessen the effects of rising temperatures, especially on the most at-risk groups.
A recent key study from researchers affiliated with Arizona State University, the University of Washington, and the University of Texas at Austin uncovers how extreme heat significantly disrupts daily life, affecting everything from time spent outside to transportation choices. The paper, titled “Understanding How Extreme Heat Impacts Human Activity-Mobility and Time Use Patterns,” has been published in Transportation Research Part D, highlighting the pressing need for policy changes as cities worldwide face increased temperatures.
The research was spearheaded by Ram M. Pendyala, a professor at ASU’s School of Sustainable Engineering and the Built Environment, along with co-authors Irfan Batur, Victor O. Alhassan, Mikhail V. Chester, and Steven E. Polzin from Arizona State University; Cynthia Chen from the University of Washington; and Chandra R. Bhat from the University of Texas at Austin. This study offers a deep look into how extreme heat alters daily travel habits and time use in various socio-demographic groups, using data from the American Time Use Survey (ATUS) and National Oceanic and Atmospheric Administration (NOAA) weather data. The focus was on 11 major metropolitan areas in the U.S., including Atlanta, Chicago, Dallas, Houston, Los Angeles, Miami, New York, Philadelphia, Phoenix, Seattle, and Washington, D.C.
This collaborative research highlights the importance of understanding how extreme heat impacts daily activities and mobility to guide policy solutions addressing the growing challenges posed by climate issues. This work was backed by two major sponsored research initiatives, including a National Science Foundation (NSF) LEAP-HI (Leading Engineering for America’s Prosperity, Health, and Infrastructure) project from the University of Washington and two U.S. Department of Transportation University Transportation Centers, namely the TOMNET center led by ASU and the National Travel Behavior and Demand (TBD) center led by the University of Texas at Austin.
Impact on Daily Habits
The study indicates that extreme heat dramatically decreases the time individuals spend outdoors. During very hot days, people tend to remain indoors, scale back outdoor activities, and limit non-essential travel. For example, data reveals a significant drop in trips for leisure, shopping, or social interaction under high temperatures. Additionally, people are shifting their travel to cooler parts of the day, preferring early morning or late evening trips to escape the midday heat.
The research identifies a notable change in transportation preferences due to extreme heat. While car usage rises, the number of trips taken by walking, biking, and using public transportation significantly declines. On average, public transit usage plummets by nearly 50% on hot days as individuals seek comfort in air-conditioned vehicles. The authors stress that this trend poses substantial difficulties for cities trying to encourage sustainable transport alternatives like walking and public transit, especially as communities increasingly face extreme weather phenomena.
Challenges for Vulnerable Populations
The findings reveal that certain demographics are especially susceptible to the negative impacts of extreme heat. Low-income individuals and those without vehicles rely more on walking and public transit, leaving them vulnerable to the scorching temperatures. These groups typically have less flexibility regarding work schedules and locations, meaning they have to travel even when conditions are harsh.
While wealthier individuals reported a notable decrease in trips during extreme heat, lower-income individuals and those lacking vehicles did not experience significant reductions in their daily travel, indicating their heightened exposure and vulnerability. The study also points out that older adults face additional difficulties in adjusting their routines, potentially leading to social isolation when they stay indoors to escape the heat.
“Our research demonstrates that extreme heat intensifies existing inequities in mobility and participation in activities,” said Pendyala. “Those already disadvantaged, including low-income individuals or those reliant on public transportation, are at an even higher risk during heat waves. This emphasizes the necessity for targeted policy measures to safeguard the most vulnerable groups.”
Recommended Policies to Address Heat Concerns
In light of these results, the authors propose various policy strategies aimed at alleviating the adverse effects of extreme heat on communities. Suggestions include developing shaded public spaces, providing transportation vouchers for vulnerable individuals, and instituting “heat days” when residents are encouraged to stay indoors, exempted from commutes, and allowed to access cooling centers if their homes do not maintain a comfortable temperature. Essentially, the study suggests implementing “extreme heat” days akin to “snow” days when workplaces and schools often close to safeguard public health. Urban design improvements, such as increasing tree planting and employing heat-reflective materials in pavements, could also enhance urban resilience against the escalating heat.
“Dealing with the repercussions of extreme heat involves not only urban design considerations but also matters of equity and public health,” remarked the lead co-author, Irfan Batur. “We must act decisively to prepare our cities to protect all residents from extreme heat threats.”
Adapting to a Warming Future
As extreme heat incidents rise in frequency and intensity due to climate change, the study’s conclusions are particularly significant. They stress the urgent need for cities to weave heat mitigation strategies into their urban planning and transportation frameworks.
The research team hopes their findings will motivate policymakers to take swift actions to foster heat-resilient urban environments.
“This study emphasizes how heat can disrupt daily life and travel, particularly harming vulnerable groups,” Pendyala noted. “Our aim is to provide the necessary evidence to facilitate meaningful change.”
