DR Congo covers a rather large area, and the large cities are pretty populous with shanty towns. There's also a lot of refugee camps. There's also not a developed economy meaning that there's not a huge amount of travel. You'd have a lot of people near to the River Congo, which the road doesn't really follow. Plus it's probably sensible to stay away from major highways, given the war-torn nature of the country.
There are apparently has 70.9 million people, not 60, and given that the population density is just 75.9ppl/sq mi. The (rather sparsely populated - especially away from the Pacific in the West) United States has 83 people/sq mi and the UK has 660. There's plenty of room for these people that you wouldn't see many.
Given all that, one would imagine it's pretty empty looking along the road.
