is
True when the vehicle is standing somewhere traffic with business elsewhere has to pass.
The judgement a person makes on arriving at a dead vehicle, and the one this class can answer immediately: it is a fact about the layout rather than about who happens to be queued, so it does not need time to pass to be meaningful. False when every zone the vehicle holds is on a spur or at a dead end -- which is what a spur is for.
The pair it forms with isObstructingNow is the useful one. This says is this a bad place to stop; the other says is anybody actually stuck. A policy with no delays before its decision wants this one. A policy that has already spent time getting somebody to the vehicle can use either, and the other is then the sharper question.