Driving on roadways laned for traffic.

Whenever any roadway has been divided into two or more clearly marked lanes for traffic the following rules in addition to all others consistent herewith shall apply: A. a vehicle shall be driven as nearly as practicable entirely within a single lane and shall not be moved from such lane until the driver has first ascertained that such movement can be made with safety; B. upon a roadway which is divided into three lanes a vehicle shall not be driven in the center lane except when overtaking a [and] passing another vehicle where the roadway is clearly visible and such center lane is clear of traffic within a safe distance, or in preparation for a left turn or where such center lane is at the time allocated exclusively to traffic moving in the direction the vehicle is proceeding and is signposted to given [give] notice of such allocation; and C. official signs may be erected directing slow-moving traffic to use a designated lane or designating those lanes to be used by traffic moving in a particular direction regardless of the center of the roadway and drivers of vehicles shall obey the directions of every such sign.