Have you tried not caring about how fast the other queue is moving? IF you are in a hurry then most stores have 'quick registers' for people who are buying less than 10 or some similarly low number of items. And obviously if you get behind someone with a full cart you'll be waiting a bit longer, but you can only guess about the last person in the queue. But if I'm not in a hurry and have too many groceries to go through the express lane, I don't see the point in staring at other lines and being upset if one is moving faster than yours. Over time this is one of those things that just averages out.