Just google, this is in Louisiana

http://www.dps.state.la.us/omv/Guide_DandE.pdf

RIGHT-HAND LANE
Avoid unnecessary lane changing. Stay in the right-hand lane unless overtaking and passing,
making an exit to the left, or letting another vehicle enter. However, you may drive in any lane of
an interstate having three or more lanes in one direction.
When you approach most entrance points, you will see a “merge” sign. This sign warns you to be
ready to adjust your speed or to move into the left lane, if possible. This will let other drivers enter
traffic smoothly and safely.