Perhaps this is because it's located halfway between the main campus of the university in the city and the medical campus and that it's necessary to cross it to move between them. Perhaps it's because it's made of dull grey concrete and is just narrow enough to create a feeling of oppression. Or that it has an old graveyard at one end. Or that it bridges over a valley with a 100 foot drop to a motorway below. Who knows?
Anyway, it had a glass arch with open roof added to it so that people couldn't climb over. Technically you still could, but you'd need to put a ladder in the middle of traffic to be able to do it.
Thing is, within days of the modification being finished, someone had carefully painted a red rectangle with evenly spaced lettering reading, "In Emergency, Break Glass".