I think the alert comes on if the car detects that you are straying out of your lane too often.
You can switch the Driver Alert system on or off through the information display by selecting Settings then Driver Assist then Driver Alert in the menu. When activated, the system will monitor your alertness level based upon your driving behavior in relation to the lane markings, and other factors.
I love this alert. My husband is the world's biggest rubber necker when driving. We have had many a tiff over him drifting around. No more tiffs since the MKC arrived, as it is the alert that is letting him know he is drifting now LOL. I don't have to say a word and I do believe he has been red faced on a couple of occasions.