Commuter Colleagues

I wonder what the exact protocol is when bumping into people you recognise from your daily commute away from the commute itself?

As a testament to just how small the world is, it's happened to me quite a few times. And in those situations I've managed a range of reactions from ignoring them, throwing a smile their way and striking up a full blown conversation (with the extremely rare case resulting in a full blown relationship to match). And in return all have had some pretty random responses from being blanked to reciprocation.

Whatever, it's a strange and sometimes awkward experience. Still, I can't wait to randomly bump into Chewie or Victoria...