Visual methods and systems are described for detecting alterness and vigilance of persons under the conditions of fatigue, lack of sleep, and exposure to mind altering substances such as alcohol or drugs. In particular, the invention can have particular application for truck drivers, bus drivers, train operators, pilots and watercraft controllers and stationary heavy equipment operators, and students and employees during either daytime or nighttime conditions. The invention robustly tracks a person\u27s head and facial features with a single on-board camera with a fully automatic system, that can intitalize automatically, and can reinitialize when it needs to and provide outputs in realtime. The system can classify rotation in all viewing directions, detects eye/mouth occlusion, detects eye blinking, and recovers the 3D (three dimensional) gaze of the eyes. In addition, the system is able to track both through occlusion like eye blinking and through occlusion like rotation. Outputs can be visual and sound alarms to the driver directly..
