I think you've missed to point completely here.
If when someone decides to end it all through suicide then they will do it, no matter how you much you or I, psychiatric practitioners, GP's or police using the MHA to have them sectioned try to stop them they will generally find a way to succeed even if it means using deception.
If you take them away from the railway, then they're just as likely to go & find another location be it another railway location, bridge a platform, foot crossing or even live rails or catenary to do it.
They may even choose to use a rope to hang themselves with, pills & alcohol, a motorway bridge, but you can be sure that they will find a way to succeed in terminating their life.
We need to look & answer the questions or statements "Who are we to intervene" or say "It's wrong to want to kill yourself".
Why? Who are we to extend someone's misery?
If everything has gone wrong for them, they've lost everyone in their life, no house/home, have no money and have no one to look after, no next of kin, NOTHING to live for and they are feeling so low, anxious & depressed they want to end it; Who are we to say NO you mustn't do it?
Yes! A suicide is a big shock to those involved (train/car/lorry/bus drivers, paramedics & those who attend the scene), those who witness a jumper from a high building & those who may find a heavily decomposed body or body parts and those who knew the person socially or immediate family, there's no denying that.
But shouldn't we be thinking, just like a terminally ill person, their pain, their suffering is over.
But can we stop it? No. I don't think that it we will be able to stop it 100%, humans are too devious & cunning and they'll almost always be able to achieve it some way or another.
As for the question "Should we stop it?" I'm not sure?
I wonder by intervening are we breaching their fundamental human right to choose life or death?