Investigation of the Microenvironment, Land Cover Characteristics, and Social Vulnerability of Heat-Vulnerable Bus Stops in Knoxville, Tennessee

Background and Purpose: The Urban Heat Island (UHI) caused by climate change and urbanization is increasing health risks to citizens. Demographic factors such as age, disability status, income level, and accessibility to social resources intersect with the impact of UHI to explain disparities in the health burden associated with heat. Considering that systematically marginalized populations rely more on public transit, it is essential to understand the intersection of public transit infrastructure and social vulnerability to address UHI mitigation and adaptation. This study investigates heat-vulnerable bus stops in Knoxville, Tennessee, analyzing local environments and social vulnerability. The research questions are as follows.

Q1. Which bus stops in Knoxville, Tennessee, are more vulnerable to heat?

Q2. What are the patterns of social vulnerability in the areas where the heat-vulnerable bus stops are located?

Methods: To identify heat-vulnerable bus stops and determine land cover characteristics and the presence of trees at the bus stops, satellite and ground heat and humidity measurements from the 2022 Knoxville Heat Mapping Campaign, land cover characteristics from the United States Geological Survey’s National Land Cover Dataset 2019, and bus stop data of Knoxville Area Transit from the City of Knoxville were mapped by ArcGIS Pro. Additionally, ten socioeconomic variables extracted from the U.S. Centers for Disease Control and Prevention’s 2018 Social Vulnerability Index were analyzed by Principal Component Analysis using SPSS to examine social vulnerability patterns in census tracts with heat-vulnerable bus stops. After mapping and analyzing the data, the lead author visited the identified bus stops and conducted a field investigation.

Results: The results of the study represent several key findings. First, most heat-vulnerable bus stops with the highest temperature are located in more highly developed and densely populated areas than the rest of Knoxville, i.e., areas vulnerable to the impact of UHI. Also, heat-vulnerable bus stops with the highest Heat Index are located in regions perceived as underdeveloped infrastructure, including public transit infrastructure. The average temperature of the identified bus stops was up to 36.14 °F higher than the other bus stops in Knoxville, which was expected to adversely affect thermal comfort for riders. Furthermore, most bus stops were found to have no trees or shelters. Second, the patterns of social vulnerability in terms of socioeconomic status and racial and ethnic minority status were prominent in the area where the identified bus stops are located. The cluster pattern of the estimates of the Black/African American population, minority, households with no vehicle available, people with no high school diploma (age 25+), and unemployment rate was identified.

Conclusions and Implications: This study found that bus stops, which are most vulnerable to heat, were exposed to harsh microenvironments that may adversely affect the health and safety of riders. By examining the identified bus stops at risk and the social vulnerability of the areas, this study identified areas negatively impacted by UHI effects, providing foundation data for mitigation and adaptation strategies that can better prepare cities to address community heat vulnerability within public transit infrastructure.