This color-changing road sign is being developed through a collaboration with scientists from the Fudan University in China with optics experts at the University at Buffalo in the US to help increase safety in the streets. The signs are capable of changing color thanks to a transparent film that respond according to the speed at which light is hitting the polymer microspheres on the surface. This means that the sign would change color rapidly if a driver was speeding to encourage them to slow down, which could also help to warn pedestrians if a vehicle is approaching at an unsafe speed.
The color-changing road sign was explained by Associate Professor Qiaoqiang Gan from University at Buffalo to New Atlas: "Just like a prism can split a white light into a rainbow, this microsphere coating delivers another way to selectively reflect a part of the white light and result in a colorful image. In particular, this color reflection is heavily dependent on the incident angle and/or observation angle."
Image Credit: Gan et. al., Sci. Adv. 2019