Comments are always very welcome, and I hope I am not going to come across as being defensive.
I would encourage people though to reconsider what "subject" means. In this image, along with "machines" my interest is the idea of obstruction and tension. These ideas are my "subject", not the signs themselves, which are used to convey the idea of visual obstruction, tension and dissonance.
Another concept could be found in the repurposing of the building over time, perhaps even going as far to a loss of it's "identity". That is actually what I've seen firsthand.
As for under-exposure, I don't know. It is dark, but detail does exist across all tonal ranges. Too dark? Perhaps.