Consider the following situation at the grocery store, on a normal day (i.e., not including out-of-the-ordinary cases like Black Friday) in a medium to large town (i.e., where almost no one will know anyone else in the store):
Everyone (say 4 to 5 people) is lined up behind the only open till. A cashier comes and opens the adjacent till and motions to the line of people she is open.
Is the general etiquette (rule?) that the people who change lines and arrive roughly at the same time line up in the same order as they were in the original line, or is it more like a race and people just line up in the order they arrive (which usually results in the person near the back of the original line begin first as they had the shortest path/best visibility)?