A low-cost system for detecting a drowsy condition of a driver of a vehicle includes a video imaging camera located in the vehicle and oriented to generate images of a driver of the vehicle. The system also includes a processor for processing the images acquired by the video imaging camera. The processor monitors an eye and determines whether the eye is in an open position or a closed state. The processor further determines a time proportion of eye closure as the proportion of a time interval that the eye is in the closed position, and determines a driver drowsiness condition when the time proportion of eye closure exceeds a threshold value.