Slow-moving vehicle to pull off roadway.

On a two-lane highway where passing is unsafe because of traffic in the opposite direction or other conditions, a slow moving vehicle, behind which five or more vehicles are formed in a line, shall turn off the roadway wherever sufficient area for a safe turn-out exists, in order to permit the vehicles following 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.