State highways in Oregon
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). Compared to other states, Oregon's system of numbering is slightly unusual in that there are two numbering systems used. The highway numbers, which correspond to the set of roads maintained by ODOT, are an internal system used in ODOT projects and accounting, and are typically not exposed to the public. The route numbers (Interstate, U.S., and Oregon) appear on maps and roadsigns, and are used to guide the motoring public. The two systems, while largely overlapping, are not congruent; many routes are marked over streets maintained by counties and cities (and thus are not part of the state highway system), and some sections of state highway do not have route numbers. In addition, the highway and route numbers do not agree (except in two situations - a portion of U.S. (route) 26 east of Portland is also Oregon Highway 26 (the Mount Hood Highway, which continues north on Oregon Route 35 while U.S. Route 26 becomes the Warm Springs Highway), and a portion of Oregon Route 47 between Manning and Banks which is co-signed as U.S. 26 is also Oregon Highway 47 (the Sunset Highway).
Highways and routes
The state highway system consists of about 8000 miles (13000 km) of state highways (roadways owned and maintained by ODOT), with about 7400 miles (12000 km) when minor connections and frontage roads are removed. This is about 9% of the total road mileage in the state, and includes Oregon's portion of the Interstate Highway System (729.57 mi/1174.13 km) and many other highways ranging from statewide to local importance. Each of these state highways has a number and name, often different from any local street names. For instance, the Oswego Highway, Highway No. 3, links Portland with Oregon City, and has names including Macadam Avenue, Riverside Drive, and Willamette Drive; it is also signed as Oregon Route 43 (see below for an explanation of these signed route numbers). 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.
Highway route numbers are posted alongside the road and shown on maps; these are the designations generally known by the public, and are broken into three systems — Oregon Routes, U.S. Routes, and Interstate Highways. The OTC designates the paths of these routes as they follow state highways and local roads; 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. Some portions of state highways do not have route numbers; as of 2007[update], the only regular highways (i.e. not spurs, connections, or frontage roads) without a route number on any portion are the Century Drive Highway No. 372 and Midland Highway No. 420. Every route is at least partially state-maintained.
The initial primary state highway system was designated in 1917, initially consisting of 36 numbered and named highways, 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 numbered 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 part of a U.S. Route received a number then. Starting in late 1931, the state took over maintenance of many county "market roads", which became secondary state highways with three-digit numbers; some of these were assigned route numbers in 1935, but many others remained unmarked. Over the years, both primary and secondary highways have been added to the system; the two systems were merged in early 2003. In 2002 and 2003, the OTC assigned route numbers to most segments of state highway that lacked them; the highway number was used in most cases, with the first digit changed to a 5 if the number was already in use. As of 2007[update], many of these routes remain unposted. Two highways — No. 372 and No. 420 - have no route numbers, and several others include portions without a route number; for instance the Klamath Falls-Malin Highway No. 50 carries OR 39 west of the junction with the Hatfield Highway No. 426 near Merrill, but the rest of the highway to Malin has no route number.
The route numbers were originally assigned in a pattern, with odd-numbered primary state routes running north–south, the lowest numbered route starting from the eastern part of the state and increasing heading west. Even numbered primary state routes ran east–west, with the lowest numbered route in the northwest corner of the state and increasing to the easternmost part of Oregon. Secondary state routes begin with 200. They were assigned with the lowest odd number in the east and increasing to the west; the lowest even number started in the north part of the state and increased heading south. The shield used to represent Oregon Routes consists of black numbering on a white shield in the shape of the Seal of Oregon.
Cancelled or demolished highways
The following highways were constructed and/or planned, and then subsequently demolished or cancelled. In some cases, the cancellation resulted from freeway revolts.
- Mount Hood Freeway
- Rose City Freeway
- Harbor Drive
- Roosevelt Freeway
- West Eugene Parkway
- Interstate 505
- Interstate 305
Proposed/future highway projects
These projects represent proposed new major routes within the state of Oregon. Improvements to existing facilities are not included in this list.
- Newberg-Dundee Draft EIS currently out for public view
- I-5 to OR 99W Connector
- Sunrise Corridor
- OR 62 Expressway/Freeway 
- Oregon Department of Transportation, 2006 Oregon Mileage Report, July 2007
- Oregon Department of Transportation, Oregon Transportation Commission, accessed September 2007
- Oregon Department of Transportation, Transferring Roads: Handbook for Making Jurisdictional Transfers, accessed September 2007
- Oregon Department of Transportation, Descriptions of US and OR Routes, July 2007
- Oregon State Highway Commission, Proposed State Highway System, November 27, 1917
- Oregon Department of Transportation, History of State Highways in Oregon, January 2007
- Oregon Department of Transportation, ODOT Approved Terms & Definitions, accessed September 2007
- Oregon Department of Transportation
- Oregon Highways (history of most highways)
- ORoads: Roads & Highways (detailed history of some highways)