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) The driver of a vehicle shall drive as nearly as practical entirely within a single lane and shall not move 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, the driver of a vehicle shall not drive in the center lane, except when overtaking 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 sign-posted to give notice of such allocation;
(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 direction of every such sign.
(`87 Code, § 17-214)