197 travels east of Dufur and down into the Columbia River Gorge, entering the city of The Dalles. The highway begins a concurrency with US 30, traveling north over an east–west BNSF rail line to a diamond interchange with I-84. US 197 leaves the interchange and the state of Oregon on The Dalles Bridge, crossing over the Columbia River into Washington. An ODOT survey measuring traffic volume for any average day of the year, expressed in terms of annual average daily traffic (AADT), was conducted in 2011 on US 197 and calculated that the busiest section of the highway in Oregon was on The Dalles Bridge, serving 5,800 vehicles, while the least busiest section of the highway was north of its terminus at US 97, serving 390 vehicles. Washington US 197 enters Washington on The Dalles Bridge, a steel cantilever truss bridge that crosses the Columbia River downstream of The Dalles Dam, and travels into Dallesport in Klickitat County. The highway continues north for past Columbia Gorge Regional Airport to its northern terminus, an intersection with SR 14. US 197 is defined by the Washington State Legislature as SR 197, part of the Revised Code of Washington as §47.17.382. Every year, WSDOT conducts a series of surveys on its highways in the state to measure traffic volume, expressed in terms of AADT. In 2012, WSDOT calculated that the Washington section of US 197 served between 3,700 and 6,100 vehicles, mostly on The Dalles Bridge. History US 197 within Washington was added to the state highway system in 1907 as State Road 8, later designated as PSH 8 in 1937, traveling east along the Columbia River from Vancouver to Maryhill. US 197 within Oregon is designated as a segment of The Dalles-California Highway No. 4, created as part of the initial named state highway system, adopted by the Oregon State Highway Commission on November 27, 1917. The highway traveled south from The Dalles through Central Oregon to the California state line south of Klamath Falls. Under the United States Numbered Highway system, approved by the American Association of State Highway Officials (AASHO) on November 11, 1926, State Road 8 in Washington was co-signed with US 830 from Vancouver to Maryhill and The Dalles-California Highway in Oregon was co-signed with US 97 from Shaniko Junction to the California state line. The Oregon State Highway Department created a numbered state highway system to