A number of the Mark 2A/2B/2C carriages were declassified in 1985 to become Standard Corridors (coded SK).
Northeast Corridor | Island Eastern Corridor | Capitol Corridor | Wakhan Corridor | Pan-European Corridor X | Shock Corridor | Polish Corridor | East-West Corridor | Central Corridor Rail Line | Blackstone River Valley National Heritage Corridor | Alameda Corridor | West Berlin Air Corridor | U.S. Route 48 (Corridor H) | Trans-Texas Corridor | Standard Corridor | Springwater Corridor | Red Rock Corridor | Quality Bus Corridor | Polish corridor | Persian Corridor | Pan-European corridor X | Pan-European Corridor IV | Northwest Corridor HOV/BRT | Northeast Corridor Line | Mesoamerican Biological Corridor | Hexi Corridor | H. B. Van Duzer Forest State Scenic Corridor | Eastern Transport Corridor | Corridor G | Central Corridor (Union Pacific Railroad) |