Whenever any roadway has been divided into 2 or more clearly indicated lanes, including those roadways divided into lanes by clearly indicated longitudinal joints, the following rules, in addition to all others consistent with this section, apply:
(1) The operator of a vehicle shall drive as nearly as practicable entirely within a single lane and shall not deviate from the traffic lane in which the operator is driving without first ascertaining that such movement can be made with safety to other vehicles approaching from the rear.
(2) Upon a 2-way roadway which is divided into 3 lanes the operator 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 marked or posted to give notice of such allocation.
(3) Notwithstanding sub. (2) , when lanes have been marked or posted for traffic moving in a particular direction or at designated speeds, the operator of a vehicle shall drive in the lane designated.