  Many road accidents are caused by drowsiness of the driver. While there are
methods to detect closed eyes, it is a non-trivial task to detect the gradual
process of a driver becoming drowsy. We consider a simple real-time detection
system for drowsiness merely based on the eye blinking rate derived from the
eye aspect ratio. For the eye detection we use HOG and a linear SVM. If the
speed of the eye blinking drops below some empirically determined threshold,
the system triggers an alarm, hence preventing the driver from falling into
microsleep. In this paper, we extensively evaluate the minimal requirements for
the proposed system. We find that this system works well if the face is
directed to the camera, but it becomes less reliable once the head is tilted
significantly. The results of our evaluations provide the foundation for
further developments of our drowsiness detection system.
