I think they both depend tbh. Bridges are all about height, as you want them to be high enough thay once you hit the water you'll go unconscious. Trains? You have a few options. You could touch the 3rd track which is typically high voltage, could lay your neck down on a rail so you can attempt decapitation, or you can try jumping in front of one hopefully head first.
Both are not a guarantee 100% method and can leave you severely disabled.