There is a weekly train from Wadi Halfa to Khartoum, which leaves some time after the weekly ferry from Aswan arrives. There are also buses and boxes heading south after the ferry arrives. NB If you wait for more than a couple of days in Wadi Halfa, all transport will have left and you may be stranded until the next weekly ferry arrives. If travelling south to Akasha with your own vehicle, note that this is a 145 kilometre stretch local maps are wrong and there is only one place with water along the way, just before Akasha.
