Funded by the National Institute for Occupational Safety and Health (NIOSH), this research aims to identify the individual, design, and environmental factors contributing to slips from ladders. Aim 1 quantifies how environmental factors influence frictional requirements of climbing. Aim 2 determines the individual factors that influence frictional requirements of climbing. Aim 3 will quantify the impact of ladder rung design factors on friction between shoes and rungs. Aim 4 will develop and validate a model for predicting ladder slips based on available and required friction during climbing.