The state highway system of the U.S. state of Oregon is a network of highways that are owned and maintained by the Highway Division of the Oregon Department of Transportation (ODOT).
Highways and routes
The state highway system consists of about of state highways, that is, roadways owned and maintained by ODOT. When minor connections and frontage roads are removed, that number drops to approximately or around 9% of the total road mileage in the state. Oregon's portion of the Interstate Highway System totals . Transfers of highways between the state and county or local maintenance require the approval of the Oregon Transportation Commission (OTC), a five-member governor-appointed authority that meets monthly. These transfers often result in discontinuous highways, where a local government maintains part or all of a main road within its boundaries.
Two separate numbering systems are used: routes (e.g. Interstate 84, U.S. Route 26, and Oregon Route 140) are those used by the general public, and their shields are posted on guide signs and maps. These comprise the Interstate Highways, U.S. Highways, and Oregon state routes (e.g. OR 201). Highways, on the other hand, are used internally by ODOT; they are named and numbered (e.g. Pacific Highway No. 1, Willamette Highway No. 18). The two systems, while largely overlapping, are not congruent. Many routes are signed on streets which are maintained by counties and cities, and thus are not part of the state highway system at all, e.g. OR 8, whose eastern- and westernmost portions, Canyon Road and Gales Creek Road, are not actually state highways. On the other hand, some state highways are not signed as routes at all; the Beaverton–Tualatin Highway No. 141 has an official route designation (OR 141), but remains entirely unsigned. Signed routes may comprise several highways; for instance, OR 47 is overlaid on the Mist–Clatskanie Highway No. 110, Nehalem Highway No. 102, and Tualatin Valley Highway No. 29. Likewise, highways may consist of several routes; Tualatin Valley Highway No. 29 comprises parts of OR 8 and OR 47. Every highway is fully state-maintained, and every route is at least partially state-maintained. any U.S. Route or Interstate numbers must also be approved by the American Association of State Highway and Transportation Officials (AASHTO). Route signs are maintained by the same agency as the roads they are posted along. If a local government maintains a numbered route, it signs an agreement with the state to keep the signs posted, thus keeping a continuous route for the benefit of travelers.
History
thumb|1918 state highway map
The initial primary state highway system was designated in 1917, including some designated earlier that year by the Oregon State Legislature and others added to the network by the Oregon State Highway Commission, the predecessor to the OTC. The first signed routes were the U.S. Routes, in 1926. It was not until 1932 that Oregon Routes were numbered by the OTC and marked by the Oregon State Highway Department; every primary state highway that was not already part of a U.S. Route received a route number at that time. Starting in late 1931, the state took over maintenance of many county "market roads", which became secondary state highways with three-digit numbers;