I was hoping for it to kick in, but I guess I was in the not so common situation where it detected me, but glare from the sun would make the car think I was not looking at the road every 10-15 secondsThe other option, and you probably already experienced this, would be to let the system automatically disable HFDA if it can't detect you within 5 to 10 seconds; it'll change to standard DA until it can adequately detect you again and automatically re-enable HFDA.
