From the VW self study guide:
Function
The driver's alertness is identified by analysing the way the driver is steering the vehicle. If the system identifies that the driver is about to fall asleep, then an acoustic warning is issued along with a text prompt in the multifunction display of the dash panel insert, telling the driver to take a break.
Along with the way the vehicle is being steered, data about the driving situation (vehicle speed, accelerator pedal use, indicating, time of day, duration of journey, etc.) and the buttons pushed by the driver on the set-up and convenience functions (air conditioning system, telephone use, etc.) are registered and transmitted via the CAN bus to the diagnostic interface for data bus, where they are analysed. The sensors required for the system are part of the ESC system, with the software integrated in the gateway.
Operation and display
Operation
The system is activated and deactivated using the display and operating unit in the infotainment system using the entry “Assistance - Driver Alert System active”. The function is available at speeds of 65 km/h or more. Following activation, the system requires around 15 minutes to collect enough data for use as a basis for deciding whether the driver is getting tired during the remainder of the journey.
Display
When driver fatigue is detected, a message appears in the dash panel insert for 5 seconds and a “gong” sounds. If
the driver does not take a break within the next 15 minutes, the message and gong are repeated. After this repetition, there is no further message.
