Transportation is a major problem in Papua New Guinea because of the difficult terrain. Major population centers are linked chiefly by air and sea, although road construction has increased to supplement these expensive means of transport. Of some 19,600 km (12,179 mi) of roads in 2002, only 686 km (426 mi) were paved. In 2000, there were 87,800 passenger vehicles and 5,049 commercial vehicles. Papua New Guinea has no railroads. However, there are 10,940 km (6,798 mi) of waterways.
The government operates a fleet of coastal work boats, none more than 9 m (30 ft) long. The principal harbors are Madang, Port Moresby, Lae, and Rabaul. There are international shipping services by refrigerated container ships, other cargo vessels, and some passenger service to Australia, Southeast Asian and Pacific island countries, the US west coast, and Europe. The main shipping lines are government owned. In 2002, the merchant fleet was comprised of 22 ships with a total of 40,911 GRT.
Papua New Guinea had 490 airports in 2001, of which 21 were principal airports with paved runways. Papua New Guinea's national air carrier, Air Niugini, established in 1973, has undertaken most of the services previously provided by Australian lines. In 2001, 1,188,100 passengers were carried on scheduled domestic and international flights.