A recent study led by UTHealth Houston reveals that some public transport shelter designs may actually worsen summer heat exposure rather than relieve it.
Published in Transportation Research Part D: Transport and Environment, the research highlights that while public transport is often more affordable, environmentally friendly, and healthier than driving, extreme summer temperatures can make waiting for buses especially uncomfortable.
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While shelters are intended to shield riders from intense sun, rain, wind, and snow, UTHealth Houston School of Public Health associate professor Kevin Lanza says no previous research had directly measured how shelter and tree shade affect heat stress at bus stops.
“Heat stress is a combination of factors, not just the temperature you see on your phone’s weather app or your car dash,” Lanza says.
“Imagine it’s 100 degrees out. If the sun is also strong and hitting you, that continues to heat you up.”
Prolonged exposure to high temperatures, like those faced by riders waiting for a bus, can quickly lead to heat stroke, a life-threatening condition that sets in when the body’s core temperature hits 40 degrees celsius. The risk increases when high humidity accompanies high temperatures.
The research team conducted their study at 17 bus stops in Houston during a 13-day stretch of extreme heat between July 20 and August 7, 2023, when temperatures ranged from 95 to 103 degrees Fahrenheit (35 to 40 degrees celsius).
Using advanced sensors, they recorded the Wet Bulb Globe Temperature (WBGT), a comprehensive heat stress measure that incorporates temperature, humidity, solar radiation, and wind, at both shaded and unshaded locations.
Unshaded bus stop areas showed an average WBGT of 33.6 degrees celsius, indicating a serious risk for heat stress. But the study found that shaded areas, particularly those under trees, offered significant relief.
Lanza’s team also evaluated four types of bus shelters. The shelter that provided the most cooling featured a stainless steel frame with glass panels on the sides and roof. Another design, made of aluminum with translucent acrylic walls and a slightly domed roof, offered a modest reduction while a third design, with a larger dome, shallower depth, and overhanging roof, cooled the air almost double that.
“Because the enclosed acrylic walls with metal trapped radiation inside the shelter, it was like an oven, making it hotter than outside the shelter,” Lanza says.
“Study results can serve as evidence for planting trees at bus stops for maximum cooling, and if shelters are the only option, then being strategic in design.”
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