Drowsiness is one of the most common causes of accidents. This is why Mercedes experts have developed the ATTENTION ASSIST system which forms part of the standard equipment of the new Mercedes CL-Class. The system continuously monitors more than 70 different parameters in order to identify driver drowsiness and provides a warning before the dangerous microsleep phase begins. Observing the driver's steering behavior has proved to be a particularly strong indicator: several years of practical research by Mercedes-Benz have shown that drowsy drivers make minor steering errors which they often correct very rapidly in a characteristic way. This steering behavior is recognized by a special steering angle sensor. Observing the driver's eyes cannot always provide conclusive evidence of sleep since many drivers can experience micro-sleep with their eyes open.