Every year, the Washington State Department of Transportation (WSDOT) conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of annual average daily traffic (AADT), which is a measure of traffic volume for any average day of the year. In 2012, WSDOT calculated that the busiest section of SR 127 was its northern terminus at SR 26, serving 1,000 vehicles.[4] The entire route of SR 127 is designated as part of the National Highway System,[5] a highway system that includes roadways important to the national economy, defense, and mobility;[6] and as a Highway of Statewide Significance by WSDOT,[7] which includes highways that connect major communities in the state of Washington.[8]
^Staff (2012). "2012 Annual Traffic Report"(PDF). Washington State Department of Transportation. p. 141. Archived from the original(PDF) on December 24, 2013. Retrieved March 23, 2013.
^Washington State Legislature (March 12, 1913). "Chapter 65: Classifying Public Highways". Session Laws of the State of Washington (1913 ed.). Olympia, Washington: Washington State Legislature. p. 221. Retrieved March 21, 2013. A highway connecting with the Sunset Highway at or in the vicinity of the city of Ellensburg; thence by way of North Yakima, Kennewick, Pasco, Walla Walla, Dayton, crossing the Snake River at either Almota or Penawawa, Colfax, Rosalia, Spokane, Deer Park, Loon Lake, Colville, to the international line at boundary, which shall be known as the Inland Empire Highway.
^Washington State Legislature (March 19, 1923). "Chapter 185: Primary and Secondary State Highways". Session Laws of the State of Washington (1923 ed.). Olympia, Washington: Washington State Legislature. p. 627. Retrieved March 21, 2013. A primary state highway, to be known as State Road No. 3, or the Inland Empire Highway, is established as follows: Beginning at the international boundary line at Laurier in Ferry County; thence by the most feasible route in a southerly direction through Colville, Spokane, Colfax, Dayton to Walla Walla; thence in a northwesterly direction through the cities of Wallula, Pasco, Sunnyside, Yakima, Ellensburg, to a junction with the Sunset Highway at or near Virden in Kittitas County.
^Washington State Legislature (March 17, 1937). "Chapter 190: Establishment of Primary State Highways". Session Laws of the State of Washington (1937 ed.). Olympia, Washington: Washington State Legislature. p. 934. Retrieved March 21, 2013. A primary state highway to be known as Primary State Highway No. 3, or the Inland Empire Highway, is hereby established according to description as follows: Beginning at a junction with Primary State Highway No. 2 in the vicinity east of Cle Elum, thence southeasterly by the most feasible route by way of Ellensburg, Yakima, Pasco and Wallula to Walla Walla, thence in a northerly direction by the most feasible route by way of Dayton, Dodge, Colfax, Rosalia, Spokane and Colville to the international boundary line in the vicinity of Laurier.
^Staff (1970). "Annual Traffic Report, 1970"(PDF). Washington State Highway Commission, Department of Highways. p. 132. Archived from the original(PDF) on October 17, 2013. Retrieved March 23, 2013.
^Staff (1980). "Annual Traffic Report, 1980"(PDF). Washington State Department of Transportation. p. 130. Archived from the original(PDF) on March 18, 2011. Retrieved March 23, 2013.