Took this route back north after a bad experience crossing at Rosso. But the drive on the Mauritanian side isn't for the faint hearted. I managed it in a front wheel drive motorhome in dry weather. Be prepared to be shaken around and give yourself 3-4 hours to do the 40km drive down the dirt road plus another 2 hours or so for the border itself. 4X4 only unless after long period of dry weather.