Not a great one to answer this one myself - my daughter will be 4 in 3 months and still wears a diaper at night. It has NEVER been dry!
If she falls asleep in the car - even for 30 minutes. I have friends whose children took a diaper off at 2.5 and went cold turkey night and day.
I don't know whether to attribute it to laziness and fear of changing sheets at night or to my pediatrition who said to me:
"Can you teach your daughter to do tricks in her sleep" me - "no" - her "well, peeing in their sleep in an unconcious activity, so unless you can teach her to do things in her subconcious, or while she is sleeping, there is not much you can TEACH her to do, unless she is ready." She told me it is completely normal, and some kids it takes until 5.
However, I have heard that getting up and taking them several times during the night helps - but I have also heard, if there diaper stays dry 2-3 nights in a row, then they CAN do it.
I am just not sure since mine can pee if she goes to sleep for 30 minutes in the car. Almost like her body just naturally relaxes.