When any highway has been divided into two or more clearly marked lanes for traffic, (1) 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 ascertained that such movement can be made with safety, and (2) the Office of the State Traffic Administration may erect, on state highways, and local traffic authorities, in accordance with standards approved by the Office of the State Traffic Administration, may erect on highways under their jurisdiction, signs directing slow-moving traffic to use a designated lane or, with signs, signals or markings, may designate those lanes to be used by traffic moving in a particular direction regardless of the center of the highway, and drivers of vehicles shall obey the directions of each such sign, signal or marking. Violation of subdivision (1) of this section shall be an infraction.