AUTONEWS

Scientists explain how car color affects city temperatures

A vehicle’s color can directly affect the air temperature around it. Dark cars heat the air around them, raising temperatures in cities. Light-colored cars reflect sunlight, offering a simple way to cool down streets, a new study has shown.

“When you walk past a parked car on a hot day and feel the heat radiating off it — it’s real, it’s not your imagination,” Marcia Matias of the University of Lisbon told New Scientist.

Marcia Matias and her team monitored two cars, a black one and a white one, left outside for more than five hours under clear skies while the air temperature was 36 degrees Celsius. The black car increased the air temperature nearby by as much as 3.8 degrees compared to the asphalt, while the white car caused no significant change.

Scientists have shown that car color significantly influences urban temperatures, with dark-colored cars increasing local air temperatures, while light-colored cars have a much smaller impact by reflecting more sunlight. This happens because darker surfaces have a lower albedo, meaning they absorb more solar radiation and convert it into heat. A study in Lisbon found that dark cars raised the air temperature by up to 3.8°C compared to the surrounding asphalt, demonstrating how parked vehicles contribute to the urban heat island effect. 

How Car Color Affects Heat

Dark Colors (e.g., black):

These surfaces absorb more sunlight, have a lower albedo (reflectivity), and consequently, convert more solar energy into heat. This makes them act like local heat sources, warming the air around them. 

Light Colors (e.g., white, silver):

These colors have a higher albedo, meaning they reflect a larger percentage of incoming sunlight. This prevents them from absorbing as much heat, keeping the surrounding air cooler. 

Impact on City Temperatures 

Urban Heat Islands: Millions of cars parked across a city can act as numerous small heat sources, exacerbating the urban heat island effect. The collective effect of their color can shift how hot streets feel.

Measurable Temperature Differences: A dark car can significantly heat the surrounding air, as demonstrated by a study in Lisbon that showed a 3.8°C (6.8°F) rise compared to the asphalt.

Implications and Solutions

Urban Planning: Incorporating the albedo of parked vehicles into urban planning strategies is essential for understanding and mitigating urban heat. 

Mitigation Strategies: Color-based parking restrictions: Limiting dark-colored vehicles in certain hotspots can help reduce heat absorption. 

Promoting light colors: Encouraging the use of lighter-colored vehicles can create cooler surfaces and lower near-surface air temperatures. 

Shading: Constructing shading elements in open parking spaces provides a physical barrier from direct sunlight. 

Why color matters...White reflects 75–85 percent of sunlight, while black reflects only 5–10 percent. Thin steel or aluminum car bodies heat up faster than thicker asphalt, amplifying local warming.

“Now imagine thousands of cars parked around a city, each of which acts as a small heat source or heat shield. Their color can actually change the temperature on the streets,” explains Marcia Matias, one of the authors of the study published in the journal “City and Environment Interactions”.

According to the report, repainting dark cars in lighter shades could increase the reflectivity of the surfaces from 20 to almost 40 percent in areas where parked cars take up more than 10 percent of the roadway, reports the portal “Zimo”.

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