I don't know if this option is available in TRS22 as I only have TRS19, but in your Trainz Settings (Performance tab of the game Launcher OR Video Settings within the game) can you see an option called "Process objects behind camera"?
If it is not ticked, tick it and see if that solves the problem.
The bridge is so large that when the camera gets close, some parts might fall behind its plane of view, so the game stops rendering the whole object. That's my simplistic theory which could, of course, be wrong.