Head-mounted display (HMD) based immersive virtual environment (VE) systems that incorporate a wearable rendering unit allow users to navigate within virtual worlds through natural walking. Redirected walking (RDW) is a technique that allows users to explore virtual worlds which are larger than the physical tracking area. It involves imperceptibly rotating the VE that the user sees, which causes the user to subconsciously compensate by physically turning. This work extends generalized RDW techniques to allow two immersed users to share a tracking area. The extension forecasts potential collisions so they can be avoided by using RDW techniques. In simulations based on recorded user-data, unsafe situations which could result in a collision occurred at a rate of 31.5/hr. in baseline experiments. The algorithm presented here resulted in all potential collisions being predicted in advance. Once predicted, most future collisions could be avoided using RDW techniques. Some, however, were resolved by stopping one or both users. These instances occurred at a rate of only 2.5/hr.