You probably need to expand your point a bit more if you want to provoke a debate. Are you asking why the text on departure screens is in lower case? Do you feel that it should be in ALL CAPS? If so, why?
I can't cite any specific research but a few years ago there was a segment on
Top Gear of all places where they went into a bit of depth about the redesign of road signs in the UK in the 1950s and 60s.
Margaret Calvert was a guest on the show, she was one of the two people in charge of the redesign (Jock Kinneir was the other but he died in 1994) and she explained that the redesign team fought tooth and nail to have most text on road signs to be in lower case because they firmly believed that lower case text is much more legible to humans at a glance because the overwhelming majority of text we read throughout the day is in a lower case font.
Calvert and Kinneir were given the task of redoing British Rail signs after they had finished with the road project. They created the now famous Rail Alphabet font and no doubt they had a large influence on the removal of signage which displayed information in ALL CAPS.
So maybe that is why the departure screens at Preston are in lower case. Maybe whoever gets to decide such things agrees with a
very successful design philosophy and that signage displaying lower case text is more useful to the people it is there to serve.
So why should departure screens not be in lower case writing?