Color-changing road signs featuring a new retroreflective material could make the signs more visible at night.
The thin film material created by researchers from Fudan University and the University of Buffalo is made up of polymer microspheres adhered to transparent tape. When a white light shines on the tape, the reflected color will vary based on the angle of the viewer and whether or not the light is moving. In a test of the film on a speed limit sign illuminated by a stationary white light, the color of the sign seemed to change from the driver’s perspective—with a faster flicker of colors indicating a faster speed. The tape could also be applied to curbs to alert pedestrians to rapidly approaching cars at night.