Robot helps L.A. to cool down

Los Angeles’ ambitious plan to cool the city as the planet grows warmer is getting a boost from a street-smart robot named MaRTy, which can measure surface and air temperature, wind speed and humidity.

Researchers from UCLA and Arizona State University have completed the first on-site evaluation of Los Angeles’ Cool Streets program, one of several sustainability strategies outlined in the city’s 2019 Green New Deal.

By covering several blocks of road with a solar reflective coating engineered to reduce surface temperatures, the city’s pilot program aims to test the cooling effects on an entire neighborhood.

“Once you take things down to the street level, arguably you have to start thinking about the thermal load on people,” said V. Kelly Turner of the UCLA Luskin School of Public Affairs, in a statement.

The reflective coating aims to prevent asphalt from retaining heat, which contributes to the “urban heat island effect” that keeps cities from cooling down, even in the evening, explains the statement. However, the paint’s highly reflective properties can actually elevate pedestrians’ exposure to heat.

To collect their cool pavement data, the researchers took robot MaRTy, which features meteorological sensors, for a spin on the streets of two Los Angeles neighbourhoods chosen for the pilot project.

In addition to measuring surface and air temperature, wind speed and humidity, the robot collects information on long- and short-wave radiation to determine mean radiant temperature, which is a reliable predictor of thermal comfort for humans. MaRTy is also nimble enough to trundle along sidewalks, ravines or other locations where a pedestrian might wander, setting him apart from measurement tools mounted on street vehicles.

On a day when air temperatures hit the high 80s, the research team walked the blocks of the two neighborhoods from 11 a.m. to 9 p.m. They found that the coated roadways were cooler to the touch, by as much as 11 degrees Fahrenheit, compared with nearby untreated asphalt — meaning the paint successfully lowered surface temperature, as it was designed to.

However, Turner and Middel also discovered that mean radiant temperatures at midday were more than 7 degrees Fahrenheit warmer in a five-foot-high area above the cool surfaces, compared with asphalt. In the midafternoon, that number fell to about 3 degrees.

While Los Angeles’ Cool Streets program targets roads designed for cars rather than people, the study provides useful data for agencies considering the cooling paint for playgrounds or other pedestrian areas.

Image credit: Maxx Girr via Pixabay

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