Helipad comes along nice, but that extended platform looks a bit fragile. Maybe add an extended crete part and only metal gratings along the sides, like
this? I also get the feeling it's still quite a small helipad (and perhaps too high?), it doesn't really feel right yet.
That hallway interior is getting better (though one could ask himself why hallways are cluttered with crates and boxes, perhaps that 'improves' truck navigation...) but as m0p said above, you'd want to add something to the walls themselves.
They're too linear, too long and boring. The texture emphasizes the flatness of the surface even more, there's no real contrasting areas in the texture which makes it appear more bland than it already is. I'd say, try a different texture, one with support beams pumped into it, or add support beams as geometry itself. An intend (?) with a maintenance door and such would be nice about halfway or such, too. Don't overdo such details, one or two are probably enough.
Oh, and some tire decals on the road and rust or crack decals on the walls might be nice, too. Small things but nice finishing touches.