Commons R-01

Commons R-01, also known as Commons Red, is a generic United Nations Space Command term for one of the commons modules on the port side of an Orbital Magnetic Accelerator Cannon Platform. It consists of a standard-sized rectangular room, with "islands" regularly spaced to the edges of the room. Security R-01 overlooks Commons R-01. You can also see the rails which the tram rides on. Spartan-117 rides on a tram right before The First Battle of Earth begins.

Cairo Station Commons Red
Cairo Station Commons Red was the United Nations Space Command portside commons of Cairo Station further from the bridge. During the First Battle of Earth, Covenant boarders invaded Commons Red, hampering SPARTAN-117s efforts at getting to the Covenant Bomb. Apparently, Only two Marines were sent to asset the battle.