Unconstructed. The traversable roads are Mirabel Road and River Road. Caltrans has no plans to adopt this route.
From Daniel Faigin: "River Road, as now exists between Fulton (US 101 and Mark West Springs Road) and Gurneville (Route 116) was built on top of an old SP railroad right-of-way by Sonoma County in the late 1950's. This alignment basically bypassed several secondary county roads such as Laughlin Road, Woolsey Road, Trenton Road, and the what was then called "River Road". The segment from US-101 to Mirabel Road was the proposed Route 181. At the time the "new" River Road was constructed, it was proposed that Route 116 be rerouted away from its Pocket Canyon Road alignment between Forestville and Guerneville, and routed down Mirabel Road to River Road, and then West to Guerneville."
Entire route. [CS&HC Sec. 253.1]