Air travelers to Seattle are served by the Seattle-Tacoma International Airport (Sea-Tac), the sixteenth busiest commercial airport in the United States. The airport is currently being upgraded with a new runway that will enable aircraft to land in any weather conditions. A new South Terminal and new Central Terminal and Pacific Marketplace were completed in 2004. Plans are also underway for a multi-year capital improvement project slated for completion by 2010 that will add needed capacity.
Two interstate highways serve Seattle: I-5 (north-south) and I-90 (east-west). Passenger rail service is available from Amtrak's four daily trains. Seattle is the southern terminus of the Alaska Marine Highway System; ferries transporting passengers and motor vehicles operate year round from points in southeast Alaska. Passenger rail service to major U.S. destinations is provided by Amtrak, and buses connect Seattle with U.S. and Canadian cities and with Tijuana, Mexico.
Avenues in Seattle run north and south and streets run east and west. The city center is perhaps best explored on foot. Seattle's bus- and trolley-based mass transit system, Metro Transit, operates routes throughout the Seattle-King County area, with service in downtown Seattle provided free of charge from 6 a.m. to 7 p.m. A five-year plan to upgrade facilities, equipment, systems, and services is scheduled for completion in 2007.