Heat stress mitigation by trees and shelters at bus stops

Municipalities are attempting to create safe and comfortable transit systems in the face of climate change. Herein, we determined how trees and different shelter designs impact heat stress at bus stops. Over 13 summer days in 2023, we used sensors to measure wet bulb globe temperature in the shade from trees and four different shelter designs to compare with unshaded areas at 17 bus stops in Houston, Texas. Results from multilevel linear mixed effects modeling revealed that tree-shaded areas were 3.2 °C (5.8 °F) cooler than unshaded areas (p < 0.001). Shelters provided less cooling than trees, and enclosed shelters were less effective than open designs. Further, heat stress was more than 3 °C (5.4 °F) higher under unshaded, enclosed shelters than unshaded areas outside of shelters (p < 0.001). Tree planting at transit stops may be a top option to improve heat safety, and shelters, if improperly designed, may be a form of maladaptation, amplifying health risk.