Still, no driverless car should ever let itself be in dense fast traffic to begin with. Only a human driver would ever be dumb enough to do something so stupid and dangerous.
I would expect all high speed roads to be continuously validated by the car network, mapped in detail and kept up to date by the sensors of each car as it drives it. Your car should be streaming a model of the upcoming road from the cloud and be able to fall back onto it in the event of sensor failure.
Handing over control to a human driver only works when one is actually in the car. And paying attention. And competent.
I would assume that a self-driving car would allow more than 1 space between cars when going 50 mph, and probably wouldn't be going 50 mph when there's black ice around.
Hell, most humans wouldn't be.
Then the human is no better or worse, no?
One of the improvements is that an autonomous car will avoid getting into a situation it can't dig itself out of. And, at times, it will detect those situations long before a human will.
My favorite counterexample for people like you is driving in Southern California in the rain. An autonomous car NOW is probably better than 25-30% of the drivers on the road in that situation.
For example, what if it's dense fast traffic (say, one car space between each car, 50mph) in random black ice conditions and sensors suddenly begin failing so the software no longer trusts is inputs? Based on recent good inputs, accelerating, swerving, or breaking are all dangerous, and based on the loss of "vision" continuing at current speed is dangerous. The safest thing to do might be to begin honking, flashing hazards, and slowing down very slowly, but could still be way riskier than just handing control to a human driver who (in this scenario) can still see.
I can think of tons of similar situations. I have a feeling a lot of folks who think it'll be so easy are people who have mainly experience driving in easy areas and conditions.
EDIT: I could have easily made the scenario way worse: the road is curvy, or random lanes are closing and reopening due to construction. Loss of visibility then means continuing straight has a high chance of causing a serious wreck quickly rather than maybe eventually