In my Passat it just barely taps the brakes rapidly to get your attention, I've never had it go further then that but in theory it will lock them up if you don'

In my Passat it just barely taps the brakes rapidly to get your attention, I've never had it go further then that but in theory it will lock them up if you don't respond. If it detects someone in the lane you are about to merge into, it cuts off the power steering for a millisecond, just long enough for you to notice the car in your blind spot but not long enough to prevent you from going into the lane if you really want to. It's pretty close to perfect in my opinion.