The government has increased investment in the transport infrastructure of Rwanda since the 1994 genocide, with aid from the United States, European Union, Japan, and others. The transport system consists primarily of the road network, with paved roads between Kigali and most other major cities and towns in the country. Rwanda is linked by road to other countries in the East African Community, namely Uganda, Tanzania, Burundi and Kenya, as well as to the eastern Congolese cities of Goma and Bukavu; the country's most important trade route is the road to the port of Mombasa via Kampala and Nairobi, which is known as the Northern Corridor. The principal form of public transport in the country is the minibus, accounting for more than half of all passenger carrying capacity. Some minibuses, particularly in Kigali, operate an unscheduled service, under a shared taxi system, while others run to a schedule, offering express routes between the major cities. There are a smaller number of large buses, which operate a scheduled service around the country. The principal private hire vehicle is the motorcycle taxi; in 2013 there were 9,609 registered motorcycle taxis in Rwanda, compared with just 579 taxicabs. Coach services are available to various destinations in neighbouring countries. The country has an international airport at Kigali that serves several international destinations, the busiest routes being those to Nairobi and Entebbe; there is one domestic route, between Kigali and Kamembe Airport near Cyangugu. In 2017, construction began on the Bugesera International Airport, to the south of Kigali, which will become the country's largest when it opens, complementing the existing Kigali airport. The national carrier is RwandAir, and the country is served by seven foreign airlines.  the country has no railways, but there is a project underway, in conjunction with Burundi and Tanzania, to extend the Tanzanian Central Line into Rwanda; the three countries have invited expressions of interest from private firms to form a public private partnership for the scheme. There is no public water transport between the port cities on Lake Kivu, although a limited private service exists and the government has initiated a programme to develop a full service. The Ministry of Infrastructure is also investigating the feasibility of linking Rwanda to Lake Victoria via shipping on the Akagera River.