Would you take a nap in the backseat while you ride? How much more improvement do you think it would need before you'd be willing to do that?
e.g. if it has a 99.9% chance of doing your daily commute without crashing and without you intervening, you can monitor it closely from the driver's seat for 6 months and there'll be ~90% chance that everything looks fine and you never need to intervene. But then if you start napping in the backseat on your commute, there's a 70% chance you'll crash within 5 years.