Avoiding person-to-person collisions is critical for visual field loss patients. Any intervention claiming to improve the safety of such patients should empirically demonstrate its efficacy. To design a VR mobility testing platform presenting multiple pedestrians, a distinction between colliding and non-colliding pedestrians must be clearly defined. We measured nine normally sighted subjects' collision envelopes (CE; an egocentric boundary distinguishing collision and non-collision) and found it changes based on the approaching pedestrian's bearing angle and speed. For person-to-person collision events for the VR mobility testing platform, non-colliding pedestrians should not evade the CE.