CodeMonkey
Active Member
are they comparing it to cut/cover or dual tunnel?
Cut and cover. Dual tunnel should have little effect on the surface expect the occasion of a building a fire exit or ventilation shaft.
Usually cut and cover is the prefer method for station building and dual tunnel to connect stations together. Sheppard subway was built in this manner.
One of the advantages of dual tunnel i can remember was, if the train derail or something happen, it wouldn't affect the other train in the next tunnel over.