A&C Cranberry Tunnel closed on weekends (Superstorm Sandy)

Sandy-Damaged Subway Tunnel Begins 40 Weekends of Rehab
...
So instead, A and C trains will be rerouted on weekends instead of being truncated entirely. This weekend, beginning this Friday at 11:45 pm, northbound trains will run on the F line between West Fourth Street in Manhattan and Jay Street in Brooklyn until 6:30 am Monday morning. The repairs, will sometimes affect both directions, will take place over 40 non-consecutive weekends and last 16 months. Workers will replace tracks, signals and components.

Cranberry (so named because it surfaces near Cranberry Street in Brooklyn Heights) is the third MTA subway tunnel to be shut down for Sandy repairs. (In addition to the R train tube, the G train got its overhaul last summer.) And it won't be the last-— but the agency's not ready to say which tunnel is next on the repair agenda.