Leapfrogging

Today all I seemed to do was leapfrog on the way to work. It's when I'm in the left lane, trying to do a decent speed, and I've got someone puttering along about 10-15 mph slower than anyone else on the road. I manage to pass them (always after grinding my teeth and driving along with them for ten minutes or more) and I get to go relatively fast for, oh, a minute or two. Then I catch up to someone ELSE going slow in the left lane, and the cycle repeats itself again, and again, and again, and...well, you get the picture. Very frustrating, especially when there's no way around them, because the other lanes are full of semi trucks and cars pulling trailers and the like. Which is fine, because they are in the correct lanes for their speed and vehicle type. But there is a law on the books that the left lane is for passing, and if someone is moving along way slower than they should be in this lane, then people can't pass and there is just a huge clot of slow cars moving along the expressway, with no one in front for a mile or more. Boy, does this get old fast, ha ha!