75 Pa. C. S. § 3301. Driving on right side of roadway

    (a) GENERAL RULE.-- Upon all roadways of sufficient width, a vehicle shall be driven upon the right half of the roadway except as follows:
 
(1) When overtaking and passing another vehicle proceeding in the same direction where permitted by the rules governing such movement.

(2) When an obstruction exists making it necessary to drive to the left of the center of the roadway, provided the driver yields the right-of-way to all vehicles traveling in the proper direction upon the unobstructed portion of the roadway within such distance as to constitute a hazard.

(3) When and where official traffic-control devices are in place designating a lane or lanes to the left side of the center of the roadway for the movement indicated by the devices.

(4) Upon a roadway restricted to one-way traffic.

(5) When making a left turn as provided in sections 3322 (relating to vehicle turning left) and 3331 (relating to required position and method of turning).
 
   (b) VEHICLE PROCEEDING AT LESS THAN NORMAL SPEED.-- Upon all roadways any vehicle proceeding at less than the normal speed of traffic at the time and place and under the conditions then existing shall be driven in the right-hand lane then available for traffic, or as close as practicable to the right-hand curb or edge of the roadway, except when overtaking and passing another vehicle proceeding in the same direction or when preparing for a left turn at an intersection or into an alley, private road or driveway. This subsection does not apply to a driver who must necessarily drive in a lane other than the right-hand lane to continue on his intended route.