This research devises a risk indexing method to assess the occupational health and safety (OHS) hazards associated with major sources of energy in the construction field, providing numerical inputs to project plan and schedule optimization. Further, the problem of “minimizing project schedule at lowest safety risks” (MPSLSR) is formalized to incorporate the concept of energy sources for OHS management in project planning and scheduling optimization. Instead of following commonly applied techniques to solve multiobjective optimization problems, the proposed research takes an alternative two-step approach to minimizing project duration and risk index, based on interpretation of path float in connection with the critical path method. This results in optimized project schedules that mitigate the substantial increment of OHS-related risks due to accelerating construction progress on projects through avoiding the incurrences of unnecessary activity time crashing and associated increases in OHS-related risks. The research application is demonstrated with (1) a tunnel construction project and (2) a made-up project featuring a large, complex network model.