Hi
I think the level at which you lose consciousness varies from person to person. I once got so hypo, I was vomiting, couldn't see properly, couldn't remember my address or simple words like 'spoon' or 'table'. No usual hypo symptoms, thought I was having a stroke. Went to hospital and my BG was so low they said most people would be unconscious at that level, I must have a very low threshold for going under. Didn't tell me the actual reading but it was long before BG machines, only had visual BM sticks, so it wouldn't have been very precise number.
With regards to driving, best to remove keys from ignition, put them on dashboard, then get into back seat while you test/eat/recover. Or get out of car if safe. Then it's clear you were not going to drive whilst hypo. If hypo in front seat with keys handy police may still try to prosecute. Don't drive until about 15 minutes *after* your BG has returned to safe level, your concentration can still be affected during this time.
Sue
Type I for 35 years