Neat find there with that blog--thanks for the link!
What is the deal with Oregon 10 (and 99E for that matter)? The GIS files show only portions of the road under state control. Does Oregon have signed routes on locally maintained roadways? From what I have read, that is the case with some of U.S. 26 between I-405 and the Ross Island Bridge.
Yes, that's a very common arrangement with highways routed along surface streets in the Metro Area. I know with reasonable certainty that OR-10 west of Murray Blvd, all the way to the terminus at OR-219 is under the control of the Washington County Department of Land Use and Transportation. The county completely funded the widening projects between Murray and Kinnaman that occurred between the mid-1990s and now. I believe the section between there and OR-217 is under City of Beaverton control.
OR-210 (SW Scholls Ferry Road) is also almost entirely under Washington County control. OR-8 in Forest Grove, between OR-47 and B Street (the old alignment of OR-47) is under City of Forest Grove control, and the section west of B Street out to OR-6 is under county control as well.
One of the best ways to tell who controls what road is by looking at the fonts, size and text alignment on the "limitless" speed signs, believe it or not. ODOT's speed signs have a distinctive style that the counties and cities generally don't use.
-Alex (Tarkus)