Transport in Sri Lanka is based on its road network, which is centred on the country's commercial capital Colombo. A rail network handles a portion of Sri Lanka's transport needs. There are navigable waterways, harbours and three international airports: in Katunayake, north of Colombo, in Hambantota, and in Jaffna. Road Roads account for about 93 percent of Sri Lanka's land transport. In October 2013, there were of A- and B-class roads and of expressways. The main modes of transportation in Sri Lanka are bus, motorcycles and passenger cars (including taxi service). Classification Sri Lanka's roads are graded E, A, B and C. Expressways The Colombo–Matara Expressway is a motorway linking Colombo, Galle and Matara which was built in 2011 to develop the economy of the Southern Province. The Colombo–Katunayake Expressway, Colombo-Kandy Expressway and Outer Circular Expressway (Colombo bypass road) are under construction, and a Colombo–Padeniya expressway has been proposed. The Sri Lankan government has proposed three elevated highways connecting the three main expressways: From Kirulapone to Kadawatha (about 19 km), connecting the Outer Circular Expressway at Kadawatha and the Colombo–Katunayake Expressway at Peliyagoda From Colombo Fort to Kottawa (about 21 km), connecting the Colombo–Matara and Outer Circular Expressways at Kottawa From Colombo Fort to the Peliyagoda interchange on the Colombo–Katunayake Expressway (about 5 km) National highways Sri Lanka's national highways are graded A or B. A-Grade roads are subdivided as AA, AB or AC. Road density is highest in the southwest, particularly the area around Colombo. Highways are in good condition, with a smooth bitumen surface and road markings; however, some rural roads are in poor condition. Heavily travelled roads are being upgraded and repaved. Public transport is widely available in many rural areas. Buses Buses are the principal mode of public transport. Service is provided by the state-run Sri Lanka Transport Board (SLTB) and privately owned buses. The SLTB has urban and rural routes; in many rural areas, it provides service which would be unprofitable for private operators. Colombo has an extensive, bus-based public transport system, with the Central Bus Stand in Pettah as its hub. The city's road network consists of radial links (or arterial routes), which link the city and district centres, and orbital links intersecting the arterial routes. Most bus routes are on the radial links, without dedicated bus lanes due to high peak traffic volume. A BRT system for Colombo has been proposed but not