what could it be when you're driving a car in after you break your hear a thunk
1 Your seat may vibrate in some cars with drowsiness alerts. 2  Drowsiness alerts are designed to warn you that you have become drowsy after you have already begun driving; you shouldnât get behind the wheel in the first place if you know youâre drowsy.  Choose a safe, secure location to take a break.
WHAT YOU NEED TO DO. Watch, listen and feel for cues from your drowsiness alert system that you may have become drowsy behind-the-wheel. Drowsiness alert systems display a coffee cup and message on your dashboard to take a driving break if it suspects that youâre drowsy.