The unspoken rule with us is he who sits in the front reads the map. This usually works at first, sits there with map open and finger resolutely stuck on our current location. Then it goes wrong, 20 minutes and a critical junction later the finger is still on the same spot or he's trying to find the small village in Cornwall that he stayed in his childhood. This results in up going round roundabouts 12 times before sending up back to Caen.