A train is going towards you and a million other people
You can just step off the track, by taking a single step, and the train doesnt hit you. Everybody else (functioning adults) can make that decision. No one actually needs to die, because everybody can avert death by taking a single step. Only the people that choose to stay on the tracks (who could have taken the step btw) die.
However, if more than 50% of the people stay on the tracks, the train magically stops, and no one dies.
Do you stay on the tracks or leave them?