long and short train

[PJW]

What problem happens operate long train and short trains in track circuit of system???

Are you referring to the issue of who the maximum an minimum TC lengths are constrained and the issues with physical stagger of block joints?

If that is not what you are asking, please let me know.

Peter

Thank you.

My problem is ambiguous.

I would like to ask long length train and short length train running in same rail system, what problems happen?

Mainline railways tend to have trains of all sorts of lengths and this generally don't give too many problems. However layout design is a bit of a compromise; to accomodate long freight trains we need to ensure adequate standage which can mean that signals cannot be placed in what would otherwise be the optimum position for layout risk / overlap length / signal sighting.

Metro lines often have one particular train length / formation. They are also far more constrained re physical space and the need for much more capacity. I believe that a mix of train lengths and types is a much greater problem.
a) For one thing if the platforms have platform screen doors then the doors on the platform must match up with the trains. If a shorter train formation is used then there wil be a platform door that must NOT open when the train arrives or else passengers go through it and fall onto the track.

b) However it is more than that; to squeeze the maximum capacity from a system then the position of the rear of the train is crucial as it defines how close the signal in rear can be placed (just outside the overlap).

c) Similarly London Underground tends not to use sectional route release in the way that Network Rail does and detects the front of the train as a cross-check that the train detection section just vacated by the rear of the train really is clear; obviously a mix of train lengths makes that excessively complicated as well.

Is this the sort of thing you were meaning?;
it would help us to understand if you explained what gave rise to you asking the question.