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Active Monitoring for Overtired Drivers
Distraction and fatigue are responsible for a lot of traffic accidents, particularly the more serious ones. Driver distraction is a major concern among traffic-safety experts. Passive car safety has increased considerably thanks to driver assistance systems, airbags and other technology and has resulted in significantly fewer injuries. However, distracted drivers are responsible for a rising number of accidents. According to insurance statistics, distraction is the cause of some 10% of accidents. Fatigue has an even greater impact on accidents: According to estimates of the Berlin-based German Insurance Assn., the umbrella organization for private insurers in Germany, overtired drivers are responsible for one in four highway accidents.
In its effort to reduce the number of accidents and fatalities, the automotive industry is turning increasingly to systems that warn drivers, in time, of dangerous actions and lack of concentration. Infrared light sources for interior camera systems and sensors already integrated into the vehicle play a central role in this new development.
Several years ago, the first systems emerged that warned drivers of fatigue or directed their attention to what is most important in a car: driving. These solutions draw their information from sensors already integrated into the vehicle for other purposes. One example is the steering-wheel-angle sensor, which primarily supplies the electronic stability program with data. This system also can detect the frequent occurrence of slight or inappropriate steering motions which indicate lack of concentration or fatigue.
For example, in the case of the notorious “microsleep,” an overtired driver holds the steering wheel almost totally motionless. As soon as he wakes up again, he gives a slight start. Analyzing signal and pedal activation, the latter via the pedal sensor, also can provide information on driver fatigue. The outwardly directed camera behind the rearview mirror mainly serves other driver assistance systems, such as the lane-departure-warning system. But the information that the car has nearly left the lane several times unintentionally over the last few minutes likewise can be used to warn a driver that his driving ability may be impaired.
Systems that actively monitor the driver are poised for full-scale production. For this application, a camera and an infrared light source are installed in the combination instrument near the tachometer. In this scenario, the camera focuses continuously on the face of the person behind the wheel.
In order to ensure the camera is operational in all light conditions, 940-nm infrared LED light sources are used so the system can operate in the dark or in different daylight situations. The driver is discretely illuminated with infrared light so he cannot see it, so he is not distracted by the light. A software program analyzes the camera image specifically in terms of the driver’s eyes.
For example, the blinking of the eyes, above all the frequency of blinking, provides information on how fatigued a driver is. Furthermore, if a driver looks to the side frequently and for a long period of time on a straight road, this can be an indication of lack of concentration on what is happening in front of the car. One challenge in this connection is analyzing the camera images: If a driver wears glasses or, even worse, sunglasses, more advanced software and higher-powered cameras are required to monitor the eyes.
In the above cases of fatigue and distraction, the system can trigger a warning to the driver. The auto manufacturer determines what kind of warning signal is given: Subtle to penetrating warning tones are just one possibility. A vibrating steering wheel is another way to warn a driver of his lack of concentration. Light strips with LED light sources on the lower edge of the vehicle windows also would be conceivable for directing the driver’s attention to the front, to what is happening on the road ahead of him.