Slipping on Concrete: A Case Study

The notion of slipperiness is rarely associated with a concrete walkway. The aggressive nature of this surface invariably satisfies the classical criterion of a safe floor. The case study described in this paper challenges this preconception. It involves a woman who enters an indoor stairwell of a parking lot and slips on the dry concrete landing while approaching the stairs with her arm outstretched to grasp the railing. The current state-of-the-art of human slipping provides this victim with no remedy at law. This paper presents a forensic and safety study that focuses on slip and fall. Slip is usually analyzed by a classical system that has no redeeming features. This protocol provides a go/no-go criterion that proclaims a walking surface safe if its interaction with a surrogate material (e.g. leather) produces an average coefficient of friction greater than 0.5. It turns out that many walkers slip on such mythical “safe” floors. The subject case adopts a modern theory of human slipping that quantitatively predicts the number of walkers who will slip on a given surface including concrete landings.