Additionally, CA also specifies the 2 lane highway, but not speed limit.
Here's the CA law again for reference:
Turning Out of Slow-Moving Vehicles
21656. On a two-lane highway where passing is unsafe because of traffic in the opposite direction or other conditions, a slow-moving vehicle, including a passenger vehicle, behind which five or more vehicles are formed in line, shall turn off the roadway at the nearest place designated as a turnout by signs erected by the authority having jurisdiction over the highway, or wherever sufficient area for a safe turnout exists, in order to permit the vehicles following it to proceed. As used in this section a slow-moving vehicle is one which is proceeding at a rate of speed less than the normal flow of traffic at the particular time and place.
Amended Ch. 448, Stats. 1965. Effective September 17, 1965.