FYI: The vast majority of people in Papua New Guinea travel, as they have always done, on foot or by canoe. Scattered population, rugged and swampy terrain, many hundreds of islands and unfavorable climatic conditions make the provision of transport difficult and expensive. The first roads were built in the late 19th century to extend the control of the colonial Administrations. Water transport was important in carrying expatriates, plantation laborers, policemen, carriers and freight until the advent of aircraft in the 1920s. Today PNG is relatively well provided with transport infrastructure. However, most roads, bridges, ports and airstrips were constructed prior to 1980 and in general have not been adequately maintained or developed to keep pace with increasing traffic and cargo. As a result, many national, district and rural roads are impassable when wet and in poor condition when dry. The most important sea port at Lae has frequent delays. The high cost of air travel and air cargo restricts the use of air transport for agricultural products, particularly perishable items such as vegetables and seafood. Sea and air navigational aids have also been allowed to deteriorate. Foreign aid is commonly the only source of funding keeping important roads, sea ports and airports in operation. The failure to maintain roads, bridges, sea ports and airstrips is a constraint to market agricultural produce and to economic growth.