[ardecila]

Presumably the idea is to allow for an efficient transfer between Ogilvie/north end of Union Station and the Blue Line. If you're at Ogilvie and exit to Randolph, Clinton or Clark/Lake are pretty far away.

Unfortunately the subway was not built to interface with commuter terminals and it's far too expensive to add that in now. The more interesting question is why the Blue Line-Metra transfer at LaSalle is still so crappy.

I think I mentioned this earlier, but the original plan was to feed the Lake Street line into the Blue Line subway, which would have included an underground station at Clinton to replace the elevated one. The station would have been set up such that Blue Line trains could not stop there.