Now, the versions I had previously been exposed to supposed that all the people were standing where they stood of their own free will. The link above suggests they have all been tied to the tracks by another person.
I'll look at those circumstances separately.
In the case of no one being tied to the tracks, the 5 people made the choice to stand where they stand, as did the one on the other tracks. Perhaps the one was smarter in his choice. It would be wrong, in my opinion, to sacrifice him because others made a bad choice and he did not. Not that standing on any tracks at any time seems particularly wise to me.
I do believe you have a responsibility to be aware of your surroundings. Failure to do so, staying in "condition white", as they say, has consequences.
I would do my best to alert everyone, and send the trolley down the tracks least likely to have anyone standing on them by the time the trolley got there.
I do not believe it would be right to toss an innocent bystander onto the tracks to save "the five", because, once again he was not among those unwisely standing on tracks. Let natural selection weed out people who stand around on trolley tracks in "condition white". OK, maybe that's a little harsh, but if you weren't present to intervene, nature would take its course anyway.
Since I don't believe rights are additive, I don't think 5 people have more rights than one. Pick any individual among the 5 and he is equal to the one. It's like saying it is "more wrong" to kill one individual five times than to kill him once. Each person only dies once and that applies to each of the six individuals in this scenario. I also don't believe in the notions of "greatest good", "general welfare", or "common good"- especially as applied to scenarios like this.
What if all the innocent people are tied to the tracks? I wouldn't waste time flipping switches or pushing people onto the tracks, I would be working to defeat the Kobayashi Maru scenario without violating the ZAP. If nothing else, self sacrifice by jumping on the tracks would be right, while pushing someone else onto the tracks would not. If the victims are tied to the tracks, is there anyone who can cut the ropes? Who are they nearer; the 5 or the one? If halfway between they could probably free one person faster than 5 so sending the trolley toward the one has a higher chance of saving everyone.
In reality there are always 3rd options. And often 4th and 5th. Why not send the trolley toward the one or ones who are most likely to be able to jump clear or be rescued by a bystander? Why not shout a warning? It is an artificial constraint to claim you can only do A or B. I think that pretty much invalidates any "answers" arrived at.
These sorts of philosophical questions are contrived to make you feel bad.
Just follow the ZAP and you'll do OK.