Upon all roadways, all vehicles proceeding at less than normal speed of traffic at the time and place and under the conditions then existing shall be driven in the right hand lane then available for traffic, or as close as practicable to the right hand lane, curb or edge of the roadway, except when overtaking and passing another vehicle proceeding in the same direction or when preparing for a left turn at an intersection or into a private road or driveway. (1956 Code, Sec. 14-44)