Imagine taking a bus on a hot summer day. The sun jumps down violently, so you hurry to the bus shelter. After all, the shadow of the structure should relieve thermal stress. However, new research shows that this is not always the case. In fact, sometimes it has made an already unpleasant situation worse.
Researchers at the University of Texas Health Sciences Center measured heat stress at bus stops in Houston between July 20 and August 7, 2023. As detailed in a study published earlier this year in a Transportation Research study, their transport study section: Transportation and the Environment, they found that on average, trees on average would reduce the average heat as the best bus shelter, and in some cases it was a bus shelter, and one person actually reduced the heat. Their findings have a direct impact on public health, especially how experts should design future bus stations.
“Thermal pressure is a combination of factors, not just the temperature you see on your phone’s weather app or on a car dash,” said co-author Kevin Lanza at the University of Texas Health Sciences Center in Houston. “Imagine it’s 100 degrees. If the sun is strong and hits you, that will continue to heat you.” The statement said standing at extremely high times for a long time puts people at risk of a thermal stroke, which increases with high humidity.
The team claims its study is the first to study how shelters and trees at bus stops affect thermal stress through ground measurements. The team surveyed the trees and four different bus shelter designs at Houston Bus Station 17 to collect data from shaded and unshaded areas, reaching temperatures of 95 to 103 degrees Fahrenheit (35 to 39.4 degrees Celsius). They were taken into account with variables of day, sheltering design and canopy, and recorded wet ball bulb temperature (WBGT) – measuring thermal stress to take into account temperature, humidity and wind.
According to their results, it is no surprise that the average WBGT in the unshaded area located in the shadow is 92.5 degrees Celsius, which usually reduces WBGT. Tree Shade lowers the WBGT by 5.9 degrees F, and the stainless steel frame with roof and glass walls also lowers it, which is the most effective cooling. By comparison, bus shelter with aluminum frames, moderate roof and translucent acrylic walls lower the WBGT by 1.6 degrees. Another similar design has a larger and shallower dome, with a draped roof and lowers the WBGT by 2.9 degrees F.
“Because the enclosed acrylic wall has metal radiation inside the shelter, it is like an oven that makes it hotter than the one outside the shelter,” Lanza said. “The results can serve as evidence for planting trees at the bus stops to maximize cooling, and if the shelter is the only option, it is strategic in terms of design.”
In short, this latest study adds a lot of evidence that cities’ trees are almost always a good idea.
