P.R. Laws tit. 9, § 5151
All vehicles shall be driven on the right side of the roadway, regardless of the direction. On public roads with more than a one-way lane, all heavy motor vehicles, including buses, and any other vehicle driven at a speed lower than the normal traffic speed at that place and at that time, under the existing conditions, shall be under the obligation to always keep to the extreme right-hand lane, except when overtaking and passing a vehicle traveling in the same direction or when preparing to make a left turn at an intersection or entering a private road.
The provisions of this section shall in no case be construed as to authorize driving a vehicle on the right-hand lane at a speed so low as to obstruct the normal and reasonable flow of traffic, according to the provisions of this chapter.
On any roadway divided into four (4) or more lanes for the traffic to flow in opposite directions, no vehicle shall travel to the left of the center line of the roadway, except otherwise authorized by official traffic control devices, allowing one (1) or more lanes to the left of the center of the roadway for the use of the traffic, which would otherwise not permit the use of said lanes, or except as permitted under subsection (b) of § 5152 of this title. However, it shall be understood that it is not prohibited to cross the center line when turning into or from an alley, private road or driveway.
History —Jan. 7, 2000, No. 22, § [6.01], eff. 1 year after Jan. 7, 2000.