“…Other methods monitor the driver's steering performance (reaction rates and unexpected lane departures) to warn the driver. However, despite claims that these approaches have low false alarm rates, it is also known that these methods fail to predict micro-sleeps, and there is not enough evidence to support these methods as a reliable way of measuring the driver's state of alert [6,12,13]. Fortunately, there are many behavioral changes that provide reliable visual cues of the driver's state of awareness that can be measured in a non-invasive manner with image processing techniques, namely, eye-blinking frequency and percentage of eyelid closure over time (PERCLOS, [14,15]), yawn frequency, head movement and eye-gaze, among other facial expressions.…”