The lane next to you is more likely to be slower than yours
Saw this link on Hacker News the other day: The Highway Lane Next to Yours Isn’t Really Moving Any Faster
The article describes a phenomenon unique to traffic where cars spread out when they go fast and get more compact when they go slow. That’s supposedly the explanation.
There’s a much simpler explanation that works for any queue. Let’s consider a supermarket checkout with two lines. One of them has a slow worker and will take 10 minutes. The other one has a fast worker and will take 5 minutes. You don’t know which one is which so you pick one at random.
With you will pick the slow one, of course. But let’s say you go to this supermarket every day for a year. Here’s the interesting thing: on average you will spend time in the slow queue. So if you sample any point in time where you are standing in line uniformly, with the other line will be faster.