Jonathan Lee-Confer, Ph.D., uses a tribometer to simulate the motion of a heel strike for slip resistance testing on a floor surface. Credit: Kris Hanning, U of A Health Sciences Office of Communications Signs reading "slippery when wet" frequently warn about the dangers of slipping and falling. But floors made slick by dry spills are also a significant hazard—one that's overlooked and understudied, according to University of Arizona Health Sciences researchers who developed a new way to assess floor slipperiness caused by dry contaminants.