A designated drover is the responsible person in a group of intoxicated individuals on a night out.
Unlike the 'Designated Driver' they are allowed to be intoxicated, but not to the point that they can not think rationally enough to look after their fellow revelers.
This may include, making sure all of a group get to the next destination, stay off roads, don't eat dodgy hot dogs, kebabs, etc. They may also end up having the responsibility of soothing the individual lying in a pool of their own vomit or tears....
The designated drover can be determined prior to the commencement of an outing or assumed at some point in an unfolding crisis.
"If it wasn't for John the designated drover, I don't know how we would have got home last night."
You were lucky there was a designated drover, otherwise:
A quote made famous for its use in season 1 of Supernatural. Implies that the driver of a vehicle chooses what music they and the passengers will listen to while whoever is riding shotgun must stay quiet.
Sam: You gotta update your music collection. Black Sabbath? Motorhead? Metallica? It's the greatest hits of mullet rock.
Dean: Well, house rules Sammy. Driver picks the music, shotgun shuts his cakehole
“Driver’s Heel” is an unsightly area on a shoe, where part of the heel on the right shoe is rubbed off from driving with your shoe scraping against the floor of the car while pushing on the gas pedal.
Nancy didn’t realize she had a bad case of driver’s heel on her good pair of shoes, but all her co-workers noticed and would snicker behind her back.