5 to drive!
I have never had an issue, if my levels are in 5s i don't give it a second thought unless i have IOB. With IOB then it depends on how much and what my reading was, how long the drive is, and the chances of me going low from over injecting (which is rare).
I typically wake up and my morning readings are 5-6.6mmol/l (sometimes higher, sometimes lower, but usually in this range) and i drive to work every day. I have learned that if i don't eat anything, my sugars won't raise or fall, for 4-6 hours.. Because of this, i have no worries about driving in the 5s.
If they are in the 4s i take a small amount of fast acting carbs that should only raise me up 1-2mmol/L which keeps me in a good range since my basal seems to keep me level.
Also, as far I know we (canada) have no law that says i have to have a test before driving, like running errands would be a nightmare if you are in and out of a car 10 trips in a day, testing before you drive to the next shop.
The spirit is more "do you feel ok to drive?' "is there any reason why you shouldn't be driving now?" If i can answer those with confidence then no worries here! A cop can't stop me without just cause, and if they did, there is no way of them knowing i am T1D.