The 2 second rule says you should be two seconds behind the person in front of you. In staggered riding of more than 2 people, you would be 2 seconds behind the bike directly in front of you and 1 second behind the staggered bike in front of you. Obviously, as you speed up the distances will increase.
I ride quite a bit with just one other rider. We always ride staggered and come up alongside at lights, stops, etc. Whoever is leading takes off first. This is far safer than side by side riding, which I think should not be legal.
