We've talked about the relationship between vigilance and VC (obeying the rules) before.
I don't want to take this thread up in A&S off topic, so I'm starting this one, but if you read the OP you'll find an excellent example of how paying attention is often required in order to be able to consistently obey the rules of the road. In this case, these guys were not paying attention, and, so, were not able to notice a stop sign in time to stop for it.
The point here is to counter Robert Hurst's criticism of EC/VC that we don't emphasize vigilance. The reason for that is that vigilance is inherent in obeying the rules of the road: if you're not paying careful attention for potential hazards, you cannot consistently obey the rules.
VC may stand for Vigilant Cycling as well as for Vehicular Cycling.