A driver monitoring system (DMS) is a small camera and software that watch the driver's eyes and face and warn the driver if they are drowsy or distracted. The camera sits near the instrument cluster or on the steering column. It usually uses infrared light, so it can see the face at night and through most sunglasses.
The software works on each frame of the camera's video. It finds the eyes, measures how far the eyelids are open and works out which way the head and the eyes point. If the eyes stay closed for too long, or the driver looks away from the road for too long, the system raises an alert.
Take, for example, a bus driver on a night run on the Yamuna Expressway near Agra. He looks down at his phone for several seconds. The camera sees his head turned down and his eyes off the road. The system sounds a beep and shows a message on the instrument cluster. In a fleet, the same alert can also be sent to the fleet owner, who sees how often each driver gets such warnings.
Some cars guess that a driver is tired from the way the steering wheel moves, with no camera. A camera is more direct, because it watches the eyes themselves.
The system is used in India mostly in buses and trucks, where a tired driver on a long night route is a common cause of accidents. A fleet operator can send the alerts to a fleet management system, or to an electronic logging device that records the driver's hours. Private cars sold in India have these cameras less often. The European Union requires new cars sold there to warn drowsy or distracted drivers, so carmakers who export to Europe fit these systems. India has not made it compulsory in private cars.
Most systems analyse the video inside the car. A car's own system sends out only the alert. A fleet system may also send a short video clip of the event to the fleet owner.
The system is a part of the digital cockpit. It works with driver assistance systems. For example, if the driver does not respond to the alerts, the car can brake or warn more strongly. The camera and its software are built by the same suppliers that make cockpit screens.