That's true, but what I meant by what I said was that robot-driven cars only have to, on average, be less dangerous than human-driven cars to make them a worthy thing to have.
If humans on average cause 10 wrecks per day in a given city, and robots would only cause 9, then that's 365 wrecks that aren't happening every year even though the robots are still screwing up 9 times a day.
Put another way, it's pretty arrogant and silly for us to insist that a machine be 100% failure free before we'll let it drive, when human drivers are drastically below that percentage. More than 35,000 people get killed in a year because humans screw up. In 2015 humans caused 1.13 deaths per 100 million miles traveled in the country. If we can drop that number with robots, then it's a good thing even if the robots still kill people. They're killing fewer people, and that's better than what we have now.