I do believe the same but don't think the comparison has any meaning. Any car in the traffic has to second-guess how other cars would behave, no matter whether

I do believe the same but don't think the comparison has any meaning. Any car in the traffic has to second-guess how other cars would behave, no matter whether the car has a human driver or not. If the overall traffic is actually overspeeding and trying not to be detected (can often happen when the speed limit is substantually lower), it is indeed safer to overspeed as well even though it would be illegal. Human drivers can---and will gladly---take that risk; driverless cars have less freedom to do so. If driverless cars have learned so much that it can simulate the human behavior, you can't really expect that they would be much safer. So driverless cars have to behave differently from other cars for the safety reason, and that behavior would affect human drivers. Humans will eventually adapt, but not until a substantial portion of road traffic is driverless, and meanwhile human drivers will be more vulnerable. I think roads with no human drivers will be eventually needed for safety much earlier than the driverless driving becomes a norm.