I woudl not switch it. Leave it on its route. ok 10 people will die, but if you make it go the other way 1 person will die.
Actually I press <tilde> godmode <enter> no_clips <enter> pause <enter> or something...
Ctrl + Alt + Delete "End task train.exe".
More seriosly though I don't see why I should change it? Honestly I would just leave it. If you kill one person you will always have that on your consience. I dont know, but I would have thought 10 people wont make much affect, you'll still be gutted in shock etc.