Although the highway carries much traffic on its paved sections in Nigeria, Cameroon, Uganda and Kenya, at present it is not a practical route between West and East since the central section across the Democratic Republic of the Congo consists only of tracks, which are impassable after the frequent heavy rain. The existence of dense rainforest, and the need for frequent river crossings, present huge challenges to road engineers. With no easy alternative routes, east-west trade has to go via air, or sea, and is consequently severely limited.