Trans-African Highway network
More than half of the network has been paved, though maintenance is a problem on much of that. There are still numerous missing links in the network where tracks are impassable after rain or hazardous due to rocks, sand, and sandstorms. In a few cases, there has never been a road of any sort, such as the 200 km gap between Salo in the Central African Republic and Ouésso on highway 3. The missing links arise mainly because the section does not have a high national priority as opposed to a regional or transcontinental priority.
As a result of missing links, of the five major regions—North Africa, West Africa, Central Africa, East Africa, and Southern Africa—road travel in all weathers is only relatively easy between East and Southern Africa, and that relies on a single paved road through southwestern Tanzania.
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Wars and conflicts
As well as preventing progress in road construction, wars and conflicts have led to the destruction of roads and river crossings, have prevented maintenance and have often closed vital links. Sierra Leone, Liberia, the Democratic Republic of the Congo and Angola are all in rebuilding phases after war. Wars in the DR Congo set back road infrastructure in that country by decades and cut the principal route between East and West Africa. In recent years, security considerations have restricted road travel in the southern parts of Morocco, Algeria, Libya and Egypt as well as in northern Chad and much of Sudan.
http://en.wikipedia.org/wiki/Trans-African_Highway_network