Washington has a system of state highways, called State Routes, as well as an extensive ferry system which is the largest in the nation[36] as well as the third largest in the world. There are 140 public airfields in Washington, including 16 state airports owned by the Washington State Department of Transportation. Boeing Field in Seattle is one of the busiest primary non-hub airports in the US.[37] The unique geography of Washington presents exceptional transportation needs.
There are extensive waterways in the midst of Washington's largest cites, including Seattle, Bellevue, Tacoma and Olympia. The state highways incorporate an extensive network of bridges and the largest ferry system in the United States to serve transportation needs in the Puget Sound area. Washington's marine highway constitutes a fleet of twenty-eight ferries that navigate Puget Sound and its inland waterways to 20 different ports of call. Washington is home to four of the five longest floating bridges in the world: the Evergreen Point Floating Bridge, Lacey V. Murrow Memorial Bridge and Homer M. Hadley Memorial Bridge over Lake Washington, and the Hood Canal Bridge which connects the Olympic Peninsula and Kitsap Peninsula.
The Cascade Mountain Range also provides unique transportation challenges. Washington operates and maintains roads over seven major mountain passes and eight minor passes. During winter months some of these passes are plowed, sanded, and kept safe with avalanche control. Not all are able to stay open through the winter. The North Cascades Highway, State Route 20, closes every year. This is because the extraordinary amount of snowfall and frequency of avalanches in the area of Washington Pass make it unsafe in the winter months.
It is recorded that transportation, including automobiles, planes, trains and ships, is the cause of 45 percent of greenhouse gas emissions in Washington.
