The numbers of reported accidents related to cranes are increasing during the past 10 years. Although simulation and visualization software are available for path planning of cranes, the high dynamic characteristics of on-site conditions often require re-planning the cranes path to ensure safety and efficiency. Any unpredicted objects on site should be detected and tracked in real time and the resulting information should be used for path re-planning. This paper proposes an approach for monitoring and re-planning path of cranes on construction sites using a real-time location system. Data collected from ultra wide band (UWB) sensors attached to the equipment, in addition to an up-to-date 3D model of the construction site, are used to detect any possible collisions or other conflicts related to the operations of the cranes. Re-planning algorithms are discussed to generate a new plan in real time. The advantages of the proposed approach are: more awareness of dynamic construction site conditions, a safer and more efficient work site, and a more reliable decision support based on good communications.