My wife can just about be persuaded to drive my Focus (and previously my Primera), but only with extreme reluctance and constant guidance so a rest is not an option (she normally drives a Matiz).
My mother on the other hand, with a little push, could even be persuaded to take over from my dad while he had a sleep - and that was in an Austin 1800 and towing a Sprite Musketeer!
SteveW