Transportation and communication in the Northwest Territories are difficult. Long winters close the rivers to navigation for all but two months of the year. Despite the Great Slave Railway and the Mackenzie highway system, which links Alberta to the Great Slave area, commerce, supply, and travel continue to be largely airborne. The region has scores of airfields. An ongoing northern roads program, launched in 1966, is helping to open up the area. The Liard Highway, opened in 1984, ties Ft. Simpson to the Alaska Highway. Other highways link Inuvik to the Yukon and Hay River and Yellowknife to the highways of Alberta. In winter, some frozen rivers and lakes are used for road traffic. There are also extensive telecommunications services.