However, if you think you can estimate your level of exposure from 71 drivers over 1 month, you are either bad at statistics, or your target level of safety is remarkably low. All you are doing with 71 people is making sure it's not so atrocious that you'll immediately have bad PR if you were to release it more widely. Hence the NDA.
As a simple rule of thumb FYI,
you use the rule of three. Example:
If we have 71 drivers, and they each drive 2000 miles on City Streets Autosteer. None of them have accidents. That's 142,000 miles with no accidents.
You divide the 142,000 by three- 47,000. You now have a 95% confidence that your accident rate is 47,000 miles or more. But you have
no idea what the actual rate is. It could be 47,001. It could be 17M. In fact, you can never really know what your accident rate is until you have some accidents. But you also don't need an accident if you can get enough data to go beyond your safety target.