a nice bit of UX i just noticed at polishpasazera.pl (one of the Polish train website). not sure when they added it, but it's clear that some serious thought went into it.

it reads something like:

Travel time: 6h
Number of changes: 0
Direct train cars: yes

with a tooltip that reads:

The train includes direct train cars from Katowice to Leipzig Hbf. The direct cars are: 267,268,269,270,272.

The trains CHEŁMOŃSKI 132 SAXONIA 3803 and SAXONIA 60003/132 are linked, which means there is no need to change trains.

Please make sure to take a seat in the section going to Leipzig Hbf.
screenshot of the UI described.
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