Failures in existing methods of rail operations can have catastrophic consequences. On September 13, 2008, for example, a safety violation known as a “Signal Passed at Danger (SPAD)” resulted in a collision between a Union Pacific freight train and a METROLINK commuter train, which occurred in Chatsworth, California (Melago, 2008). This collision resulted in the death of 26 people and injuries to 135 more. Another SPAD in Macadona, Texas in June 2004 resulted in 3 deaths and 30 injured when a BNSF freight train and a Union Pacific freight train collided (NTSB, 2006). A failure of a train crew to correctly line a switch in January 2005 in Graniteville, South Carolina resulted in a collision between two Norfolk Southern freight trains. The collision and subsequent release of chlorine gas caused the death of 9 people, injury to an additional 554, and the evacuation of 5400 for a period of 2 weeks (NTSB, 2005). All of these accidents, and the associated casualties, could have been prevented had a Positive Train Control (PTC) system been installed and operational.