A report written by Automotive IQ in 2016 revealed that in 2016, a self-driving car failed about every 3 hours in California.
Self-driving car manufacturers are required to report to the California DMV how many times their vehicles malfunctioned during the preceding year, a.k.a. "disengagement reports". Such incidents cover situations due to hardware or software failure or because the driver anticipated a problem.
Note: while Google/Waymo apparently stands apart with a much lower incident rate than the others, they don't report every incident but instead only those they have deemed through further simulation/analysis to have been legitimately unsafe (e.g., collision would have occurred without intervention).
In summary, in 2016 and relative to a notional average of a 60 mile commute day period, the autonomous driving hardware/software could be projected as needing to be disengaged by human (test) drivers on average once every:
85.5 days on account of safety concerns (Google/Waymo)
2.2 days on account of safety or comfort concerns (the others)
How many days has it been since your driving needed correction from another via intervention?
How often did humans have to get involved?