On the freeway, the time it takes to react to seeing the next car's brake lights isn't the main problem. The bigger problem is how long it takes to judge that car's deceleration.
Are they just tapping the brakes because the road is bending---some people always do---or are they slamming on the brakes because there's a traffic incident that you can't yet see? You're 200-millisecond reaction needs to be completely different in these two cases, but you just can't immediately tell the difference.
Both for people and for automatic cars, judging deceleration is a harder problem than just reacting to a red light going on, but the sensors on automatic cars should give them a big advantage.
Are they just tapping the brakes because the road is bending---some people always do---or are they slamming on the brakes because there's a traffic incident that you can't yet see? You're 200-millisecond reaction needs to be completely different in these two cases, but you just can't immediately tell the difference.
Both for people and for automatic cars, judging deceleration is a harder problem than just reacting to a red light going on, but the sensors on automatic cars should give them a big advantage.