I was driving up a narrow residential street at about 35 mph following about three car-lengths behind the vehicle ahead. On the right side of the lane bushes obstructed driveways from the homes behind. Suddenly, I cought sight of a van backing of a drive beyond the car ahead and the car's brake lights went on. Before I could move my foot to the brake pedal a "horn" blasted at me, a large red blob showed in the driver display and my S braked sharply. (At least that is the way I remember it.) WHEW! Obviously, at that speed none of the driver assist features were enabled. This car watches out for you.