Previous research and applications in construction resource optimization have focused on tracking the location of material and equipment. There is a lack of studies on automated monitoring of the interaction between workers and equipment for safety purposes. This paper presents a new approach for measuring the safety performance of construction personnel particularly when they work in very close proximity to moving equipment as well as static hazards such as chemical and flammable substances. A method of generating hazardous zones according to the geometric and kinematic characteristics of the considered hazard is introduced. The spatio-temporal relationships between the hazardous zones and workers positioning data collected by real-time location sensing technology are automatically analyzed. This approach has been validated in a controlled test bed environment that simulates a construction site. Results indicate that workers safety performance of selected activities can be automatically and reliably measured using the developed approach. Furthermore, a heat map is generated for visualizing proximity related issues in the test bed using the computed results.