You get a minor graphical glitch when working near a rail, ie with an inserter or box in hand, you get shown a double bracket for where the train is.
Please see attached image.
double train 'brackets' when working near rails
double train 'brackets' when working near rails
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Re: double train 'brackets' when working near rails
Not a glitch per se; one is for the location of the cars on the rails according to the station placement, the other is for the car that will be involved itself.