
Originally Posted by
Dawnstorm
So, I'm quite curious how to analyse a sentence like:
5. We changed trains at Victoria station.
so that "train" is a complement. What does it complement? Since this sentence has no object, "trains" would have to be a "subject complement". But I don't see that.
It might be an "adverbial complement"?
I'm not sure myself.
Consider that its semantic contribution is intransitive;i.e., synonymous with transfer. 
Active: We have to transfer trains.
Passive: Trains have to be transferred [by us]. 
Additionally, do you see a pattern here?
Ex: We were asked to/were told to/were made to/need(ed) to/want(ed) to transfer trains at Victoria station.