Transport in Sudan during the early 1990s included an extensive railroad system that served the more important populated areas except in the far south, a meager road network (very little of which consisted of all-weather roads), a natural inland waterway—the Nile River and its tributaries—and a national airline that provided both international and domestic service. Complementing this infrastructure was Port Sudan, a major deep-water port on the Red Sea, and a small but modern national merchant marine. Additionally, a pipeline transporting petroleum products extended from the port to Khartoum. Only minimal efforts had been expended through the early 1980s to improve existing and, according to both Sudanese and foreign observers, largely inefficiently operated transport facilities. Increasing emphasis on economic development placed a growing strain on the system. Beginning in the mid-1970s, a substantial proportion of public investment funds was allocated for transport sector development. Some progress toward meeting equipment goals had been reported by the beginning of the 1980s, but substantial further modernization and adequately trained personnel were still required. Until these were in place, inadequate transportation was expected to constitute a major obstacle to Sudan's economic development. Railways Total: 7,251 km Narrow gauge: 5,851 km 0.600m gauge: 1,400 km (2014) The main line runs from Wadi Halfa on the Egyptian border to Khartoum and southwest to Al-Ubayyid via Sannar and Kusti, with extensions to Nyala in southern Darfur and Wau in Bahr al Ghazal. Other lines connect Atbarah and Sannar with Port Sudan, and Sannar with Ad Damazin. A 1,400-kilometer line serves the al Gezira state cotton-growing region. Modest efforts to upgrade rail transport were reported to be underway in 2013 and 2015 to reverse decades of neglect and declining efficiency. Service on some lines may be interrupted during the rainy season. The main system, Sudan Railways, which was operated by the government-owned Sudan Railways Corporation (SRC), provided services to most of the country's production and consumption centers. The other line, the Gezira Light Railway, was owned by the Sudan Gezira Board and served the Gezira Scheme and its Manaqil Extension. In 1959 the railways made up 40% of the Sudanese gross domestic product but by 2009 only 6% of Sudan's traffic was carried by rail and since the 1970s competition from highways increased rapidly. Highways Total: 31,000 km Paved: 8,000 km Unpaved: 23,000 km Urban: 1,000 km (2019) Sudan remains heavily dependent on railroads, but the road network