...and the reverse liability implications: "My spouse had an asthma attack and their car didn't pull over safely, so it is the [car manufacturer]'s fault that they crashed into a tree and died."
Not being a drink or erratic driver, I was thinking more of driving when I'm tired. It is possible to be a little too tired to drive safely without realising it, but I imagine the extra small adjustments you make when this happens - because you drift and correct - would be recognisable by the car.
It would be a huge pain if you are on a long drive and your car decides you need a nap! But it would save lives, possibly mine. Personal transport is a convenience. Personal safety is paramount.