Track Etiquette

A quick glance under the armpit should be enough to make sure you don't deck anyone behind. If there's enough time a glance over the shoulder.

If no.3 hasn't moved out yet I wouldn't allow him the space to move, I'd only move up when I have to. Then again, if this isn't a group of well experienced riders you cannot trust him not to move suddenly rather than a slightly more gradual move that you can read.

Pretty sensible. Don't move from your line without looking and try to anticipate what riders in front of you may possibly do.