The transportation infrastructure in Afghanistan is notoriously abysmal. Roads are primitive and few, and regional rail networks do not even enter the country. And the U.S./NATO military machine is notoriously heavy and fuel-intensive, which makes for a mountain of logistical challenges. Although a northern distribution route has opened up, operations are sustained by an army of civilian Pakistani truck drivers who transport most of the supplies — especially fuel — for the U.S./NATO military effort. At the heart of what passes for a road network in Afghanistan is Highway 1, or the "Ring Road" (also known as the Garland Highway), which is the central artery connecting the country's four main population centers — Mazar-i-Sharif, Kabul, Kandahar and Herat. The roadway, parts of it unpaved, has existed in one form or another since before the Soviet invasion, but only since about 2003 have efforts been made to improve and complete it.