Google’s report [PDF] outlined 272 situations in that timeframe where software on its vehicles detected a problem that needed a human driver to remedy, otherwise known as disengagements, the Wall Street Journal points out.
Out of those instances, Google’s analysts determined that if a human hadn’t jumped in, there would probably have been 13 “contacts” with other vehicles or objects.
In a sign of improvement within the report, the number of disengagements declined over that period, going from once every 785 miles in the first quarter of testing to once every 5,318 miles in the most recent.
Google has the largest fleet of autonomous vehicles on public roads in California right now, but other automakers and suppliers had to make similar reports, with far higher frequency of interventions, the WSJ points out. This shows that self-driving vehicles simply aren’t ready to dive into whatever the road may throw at them without a dedicated human on standby.