the push a man variant is just stupid. obviously whoever thought of that has never seen a death scene where a person has been hit by a train. i've seen it in chicago where people get hit by the metra pretty regularly. if you push the man 6 people die instead of 5. it's a simple matter of momentum (mass x velocity). even the smallest trolley will weight 3-4 tons and a massive man would be 500 pounds making it a 12x multiplier. hell, if the man of really weighed 500 lbs it would take me longer to push the man in front of the trolley then to push the regular sized people out of the way...Of course it doesn't really work.
If there was like a 400 ton man, you wouldn't be able to move him.
There's a variation where there's a lever that drops the fat man.