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The State Highways of Washington in the U.S. state of Washington comprise a network of over of state highways, including all Interstate and U.S. Highways that pass through the state, maintained by the Washington State Department of Transportation (WSDOT). The system spans 8.5% of the state's public road mileage, but carries over half of the traffic. All other public roads in the state are either inside incorporated places (cities or towns) or are maintained by the county.〔 __FORCETOC__ ==System description== All state highways are designated by the Washington State Legislature and codified in the Revised Code of Washington (RCW). These routes are defined generally by termini and points along the route; WSDOT may otherwise choose the details, and may bypass the designated points as long as the road serves the general vicinity. WSDOT's duties include "locating, designing, constructing, improving, repairing, operating, and maintaining" these state highways, including bridges and other related structures. Within cities and towns, the local governments are responsible for certain aspects of the streets maintained as parts of a state highway, including their grade and the portion not used for highway purposes. All routes, even Interstate and U.S. Highways, are defined as "state route number" plus the number; for instance, Interstate 5 is "state route number 5" and U.S. Route 395 is "state route number 395". Also included in the RCW are "state route number 20 north" (signed as State Route 20 Spur) and "state route number 97-alternate" (signed as U.S. Route 97 Alternate). Some other spurs, such as State Route 503 Spur, are defined as part of the main routes, as is U.S. Route 101 Alternate.〔 WSDOT has also defined some spurs that mainly serve to provide full access between intersecting routes.〔The only ones listed in the 2006 log that do not provide such "missing movements" are SR 9 Spur to the truck customs in Sumas and SR 504 Spur and SR 906 Spur to WSDOT maintenance areas.〕 Although most state highways as defined by law are open to traffic, State Route 109 dead-ends at Taholah, State Route 501 has a gap in the middle, and State Routes 35, 168, 230, 276, and most of SR 171, 213, and 704, have not been constructed.〔〔 Notable sections of state highways include the six crossings of the Cascade Range - the Columbia River Gorge (SR 14), White Pass (US 12), Chinook Pass (SR 410), Snoqualmie Pass (I-90), Stevens Pass (US 2), and the North Cascades Highway (SR 20). Of the 13 public road crossings of the Canadian border in Washington, nine are on state highways. Major bridges include the Tacoma Narrows Bridge and three floating bridges: the Evergreen Point Bridge, Hood Canal Bridge, and Lake Washington Bridge. The Washington State Ferries, except the route to Sidney, British Columbia, were legally included in the state highway system in 1994; a new State Route 339 was created at that time for the passenger-only Seattle-Vashon Ferry. According to the Washington State Department of Licensing, ocean beaches are legally state highways with a general speed limit of 25 mph (40 km/h), many only open to vehicles between the day after Labor Day and April 14, but state law places the beaches under the control of the Washington State Parks and Recreation Commission and only designates them as "public highways". Most state routes are numbered in a grid, with even-numbered routes running east–west and odd-numbered routes running north–south.〔Only SR 501, SR 523, SR 531, and SR 548 run in a perpendicular direction.〕 Even two-digit routes increase from south to north in three "strips", with SR 4, SR 6, and SR 8 in the western part of the state, SR 14, SR 16, SR 18, and SR 20 along the Interstate 5 corridor, and SR 22, SR 24, SR 26, SR 28, and former SR 30 in the east. Odd numbers similarly increase from west to east, with SR 3, Interstate 5, SR 7, SR 9, SR 11, SR 17, SR 21, SR 23, SR 25, SR 27, and SR 31 following this general progression. (SR 19 was added in 1991, and lies west of SR 3; SR 35 and SR 41 are extensions of highways in adjacent states.) Three-digit routes (and SR 92 and SR 96) are usually numbered by taking the first one or two digits of a route it connects to and adding another digit or two. In some cases, instead of using the two-digit route's actual number, a number that would fit the grid is used instead. Three-digit routes have been numbered as follows: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「State highways in Washington」の詳細全文を読む スポンサード リンク
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