Aren't they already at risk of getting killed just by wandering to the neighboring tribe? Why would they go some other part Africa that's even further away? Either GTFO out Africa entirely or stay home, right?
Cargo trains make sense for a lot of reasons. But think about what a nightmare border control would be for any passenger train. Jesus. I bet some guards would stop the train for 12 hours until they find a black foreigner they can shake down for loot.