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New material can help make safer ‘retroreflective’ road signs

While driving at night or in low-visibility conditions, road sings with important information may be difficult to see.

Researchers from China’s Fudan University and University of Buffalo have developed a new film that reflects light and changes color at night when light is shined upon it. 

The hope is that this new material could be added to road signs in order to improve visibility and safety for nighttime drivers. 

“You can use this material to make smart traffic signs,” said co-first author Qiaoqiang Gan, PhD, an associate professor of electrical engineering in the UB School of Engineering and Applied Sciences. “If a person is listening to loud music or isn’t paying attention while they’re walking or driving, a color-changing sign can help to better alert them to the traffic situation.”

Boxes A-F show how the sign changes color, from the perspective of drivers on the road, as they pass by.
Image Credit: Fan et al., Sci. Adv. 2019

The film is made of polymer microspheres placed on the sticky side of a transparent tape. When white light shines on the film at night, some viewers will see a single, stable color reflected back, whereas others will observe changing colors. This depends on the angle of observation and whether or not the light source in question is moving. 

However, from the driver’s perspective, the film’s color remained stable. But to pedestrians standing on the side of the road, the color of the film appears to flicker and blink as the car’s headlights speeds past.

“If the car goes faster, the pedestrian will see the color change more quickly, so the sign tells you a lot about what is going on,” said co-author Haomin Song, PhD, UB assistant professor of research in electrical engineering.

These findings are published in Science Advances.

By Olivia Harvey, Staff Writer

Image Credit: Fan et al., Sci. Adv. 2019

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