The Trans-Sahara Highway or TAH 2, also known as the African Unity Road, is a transnational highway project nearing completion to pave, improve and ease border formalities on an existing trade route running north–south across the Sahara Desert. It runs between North Africa bordered by the Mediterranean Sea in the north and West Africa bordered by the Atlantic Ocean in the south, from Algiers in Algeria to Lagos in Nigeria, giving it the alternative names of the Algiers–Lagos Highway or Lagos–Algiers Highway. The Trans-Sahara Highway is one of the oldest transnational highways in Africa and one of the most complete, having been proposed in 1962, with construction of sections in the Sahara starting in the 1970s. Its central section is still little-used though, and still requires special vehicles and precautions to be taken to survive the harsh environment and climate of the center of the desert. Route and status Overall features, length and condition The Trans-Sahara Highway has a length of about 4,500 km of which about 85% has been paved. It passes through only three countries, since Algeria and Nigeria are separated by Niger alone. However, an additional 3,600 km of linked highways to Tunisia, Mali, and Chad are considered by planners to be integral to the Trans-Sahara Highway. All the 1,200 km of the highway lying in Nigeria is part of that country's national paved road network and includes nearly 500 km of four-lane divided sections, but highway maintenance is frequently deficient in Nigeria and at times parts of the road may be in poor condition, including having lost the pavement. About half the highway, over 2,300 km, lies in Algeria and is mostly in good condition, but particularly south of Tamanrasset much of it is in poor condition, with the last section from In Guezzam to the Niger border due for being paved in 2022. Niger has 985 km of the highway of which 785 km is paved but also in poor condition. Further details are given below. Another crossing of the Sahara is proposed for the Tripoli–Cape Town Highway (Trans-African Highway 3) but this route requires a great deal more construction, faces problems of instability and lawlessness in northern Chad, and is not likely to stimulate trade to the same extent as TAH 2. Consequently, it may be decades away from completion. Two other Trans-African Highways cross the Sahara, but at its edges. In 2005 the