u/AnimatedCowboy

I keep seeing the point that one of the biggest limitations to the B and D lines increasing their frequencies (practically, not politically) is that, when they were being built, they value-engineered out a Ventilation shaft in the Cahuenga Pass. I was wondering if this could be added now and how difficult it would be. Having very little understanding, I'm like "just dig a hole," but I'm sure it's more complicated than that (both practically, and politically). Would anyone like to opine on this Idea?