fewer chances of map reading cockups
I gave up trying to read a map and driving at the same time - also no longer let the wife look at the map and say things like 'You have to turn left somewhere up ahead', 'This road isn't on the map' and 'I think you should have turned left back there'. Just keep a list of major towns along the route, follow any signs for the same and if in doubt keep straight on. Crap advice? Maybe, but it works for me. I think the buggery bit is when you hit that bit where you have to filter right, you're trapped in the left lane and have to cut across to the right - woooaaaaahhh!

Know what you mean, this year due to last minute drop out I drove on my own. Without the aid, or interferance, of a map reader i got there and back with out getting lost once, and i got to choose the music!
The junction you are talking about I guess, is at the top of the hill just before you get into Rouen on the way home, everyone is in the outside lane storming up the hill when you need to get across sharpish to the right otherwise you have a nice trip thru Rouen city centre.