State Highways in Washington

State Highways in Washington
Standard route signage in Washington
Map of Washington's highways
System information
Length:	7,000 mi (11,000 km)
Notes:	Defined by RCW 47.17; maintained by WSDOT
Highway names
Interstates:	Interstate X (I-X)
US Highways:	U.S. Route X (US X)
State:	State Route X (SR X)
System links
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former

The State Highways of Washington in the U.S. state of Washington comprise a network of over 7,000 miles (11,270 km) 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.

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.