Title XXIII Chapter 316 View Entire Chapter
MOTOR VEHICLES STATE UNIFORM TRAFFIC CONTROL
316.081 Driving on right side of roadway; exceptions.—
Upon all roadways of sufficient width, a vehicle shall be driven upon the right half of the roadway, except as follows:
(a) When overtaking and passing another vehicle proceeding in the same direction under the rules governing such movement.
(b) When an obstruction exists making it necessary to drive to the left of the center of the highway
This can also be used as a reason for a stop.