International audienceConstruction is one of the most hazardous industries because it involves dynamic interactions between workers and machinery on sites. The recent technological developments in indoor positioning technologies provide a huge volume of spatio-temporal data for studying dynamic interactions of moving objects. The results from such studies can be used for enhancing safety management strategies on sites by recognizing the mobility related workers` behaviors. For understanding workers` mobility behaviors to improve site safety, a system is proposed based on semantic trajectories and the Hidden Markov Models (HMMs). Firstly, the system captures raw spatio-temporal trajectories of workers using an Indoor Positioning System (IPS)...