As of 2007, Uzbekistan's overland transportation infrastructure declined significantly in the post-Soviet era due to low investment and poor maintenance. Air transport was the only branch that received substantial government investment in the early 2000s, as airport modernization projects were undertaken. In the following years, improvements have been made to the surface transport network including the construction of the Tashkent–Samarkand high-speed rail line. Railways As of March 2017, the total length of Uzbekistan's main railway network is , of which is electrified. Highways As of 2005, Uzbekistan had of roads, about of which were paved. The road infrastructure is deteriorating, particularly outside of Tashkent. No significant highway projects were underway in 2006. In the early 2000s, U.S. engineers improved some roads around the port of Termez to facilitate movement of humanitarian supplies to Afghanistan. Uzbekistan is a member country of the United Nations’ Asian Highway Network, and several national roads are designated as part of the network. There are some parts of the roads considered as freeways, although mostly in a state of complete neglect and disrepair since the collapse of the Soviet Union. The ring road around Tashkent is about long, and completely multilaned, although it lacks a carriageway separation in most sections. The M39 Highway, connecting Tashkent and Samarkand is a 4-laned road in some of its length, although poorly maintained and without carriageway separation in most of its length. In January, 2017, the Kazakhstan and Uzbekistan governments made an agreement to reopen the section of this highway which passed through Kazakhstan that had been closed for ten years, avoiding the detour via Guliston. The M37 Highway starts from Samarkand, reaching west to the Turkmen border, via Navoiy and Bukhara. The A373 Highway starts from Tashkent, going east through Kokand of Fergana Region, and ends at the Kyrgyz border. Ports and waterways Double landlocked Uzbekistan has no seaports. Its main river port is Termez on the Amu Darya river. Although Termez lacks modern facilities and has a shortage of spare parts, activity there has increased as conditions in neighboring Afghanistan have stabilized. Termez has been an important transfer point for humanitarian supplies entering Afghanistan. Uzbekistan has of inland waterways. Since the mid-1990s, commercial travel on Uzbekistan's portion of the Amu Darya has been reduced because of low water levels. Pipelines As of 2010, Uzbekistan had of natural gas pipelines, of oil pipelines, and of pipelines for refined products.