20 percent of injuries are the result of surface falls. Reductions are due in part to improvement in products and materials. But slips still cause injuries and death and we can do more to understand their causes. It's hard to believe, but things are improving. The relationship of the foot to the surface is called traction or friction.
Friction is the resistance to lateral movement caused by the contact between two surfaces.
Dividing the horizontal force by vertical force, we get a number called the coefficient of friction. Concrete, with .8 COF, would have more traction, and be less slippery, than ice, with a COF of .3. COF has become one of the common performance measurements for products like floor finishes. COF even defines a legal duty. The first formal definition of slipresistant surfaces is in the proceedings of the Department of Commerce in 1953.