This may be due to there being more cars exiting the freeway from the right lane. Also, intuitively, drivers often tend to bear left to get to the "fast" lane,

This may be due to there being more cars exiting the freeway from the right lane. Also, intuitively, drivers often tend to bear left to get to the "fast" lane, but as they defect to the left lane, it frees up the center lane in a similar fashion as exits free up the right lane. My compromise in a three-lane situation is to always favor the center lane in congested traffic, especially prior to an upcoming exit. If traffic starts to move, I can move left since after the exit, the missing cars will be starting to merge back in (and to the left, negating the advantage of the center). If traffic doesn't move, I tend to just maintain center lane. Impatient, frequent lane changers always add risk to themselves and others because they're bouncing back and forth between left (the fast lane and the way things "should" be to them) and the right (which routinely frees up as people exit). They tend make it to where they're going faster, but I don't necessarily think it is worth the risk.