DAC is intended to attract the driver's attention when he/she starts to drive less consistently, e.g. if he/she becomes distracted or starts to fall asleep.
The objective for DAC is to detect slowly deteriorating driving ability and it is primarily intended for major roads.
A camera detects the side markings painted on the carriageway and compares the section of the road with the driver's steering wheel movements. The driver is alerted if the vehicle does not follow the carriageway evenly.
In some cases driving ability is not affected despite driver fatigue. In which case there may not be any warning issued for the driver. For this reason it is always important to stop and take a break in the event of any signs of driver fatigue, irrespective of whether or not DAC issues a warning.
The function must not be used to extend a period of driving. Always plan breaks at regular intervals, and make sure you are well rested.
In some cases the system may issue a warning despite driving ability not deteriorating, for example:
DAC is not intended for city traffic.
The camera sensor has certain limitations, see Collision warning system - camera sensor limitations.