RSA 265:24 Driving on Roadways Laned for Traffic.

Whenever any roadway has been divided into 2 or more lanes clearly marked for traffic, the following rules in addition to all others consistent herewith shall apply:
I. 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;
II. Upon a roadway which is divided into 3 lanes and provides for 2-way movement of traffic, a vehicle shall not be driven in the center lane except when overtaking and passing another vehicle traveling in the same direction when such center lane is clear of traffic within a safe distance, or in preparation for making a left turn or where such center lane is at the time allocated exclusively to traffic movi