At least in the Kaplan household, “designated driver” has nothing to do with alcohol, intoxication, or any illicit substances.
It’s a function of the weather.
So, when it’s exceptionally icy or snowy (it’s both today in the Twin Cities), either me or one of my sons assumes driving duty from my wife, using our 4-wheel drive instead of our minivan.
Of course, when conditions are truly abysmal — this past Saturday morning comes to mind — it’s best to stay off the roads altogether . . .
See also, “Now, THAT’S What I Call a Designated Driver!.”