Combat reality can be simulated and represented using complex, layered data and visual aides, most of which are head-mounted displays (HMD), which encompass any display technology that can be worn on the user's head. Military training solutions are often built on commercial off-the-shelf (COTS) technologies, such as Virtual Battlespace 3 and VirTra, both of which are used by the United States Army. , VirTra is being used by both civilian and military law enforcement to train personnel in a variety of scenarios, including active shooter, domestic violence, and military traffic stops. Mixed reality technologies have been used by the United States Army Research Laboratory to study how this stress affects decision-making. With mixed reality, researchers may safely study military personnel in scenarios where soldiers would not likely survive.