I believe it's how often the system requires human intervention... e.g., once per 1,000 miles, or once per 250 hours, or something like that.
Oh, that would make sense. Thanks!
Disengagement rate.
Did you honestly believe you were clarifying in a less confusing manner than the original question with this response?
The parent poster is correct though. "Disengagement rate" is the term used in the industry, and what would get you results in google searches.
"Disconnect rate" is not what it's called, so it's helpful to correct that.