If you drove with zero distance between your bumper and the car in front of you, they will be unable to brake hard, because its trying to stop an extra ton of mass. you&#x27;re fine sure, but they just ran over that kid crossing the road without looking. or just t-boned someone. and heaven forbid someone was tailgating you too.<p>autonomous cars can form trains because they can react orders of magnitude faster than a human can to suddenly changing driving conditions.