GPS-Enabled Tracking For US Railways

GPS-Enabled Positive Train Control Program Will Forever Change U.S. Railways

 

On September 12, 2008, a Metrolink passenger train collided with a Union Pacific freight train in California, resulting in the deaths of 25 people and injuring more than 135 passengers. In the midst of one of the most horrific rail fleet tracking failures in recent history, U.S. Congress drafted a bill to implement an enhanced GPS tracking communications system between a multitude of different American railway systems and their fleet tracking divisions. On October 16, 2008, President George W. Bush signed the 315-page Rail Safety Improvement Act of 2008. By building upon the existing GPS tracking technology, the Precision Train Control (PTC) program will allow for unprecedented communication among rail fleet tracking managers when it is completed in 2015.

 

While standard GPS tracking devices transmit signals from up to four GPS tracking satellites directly to a receiver, there is a margin of error as these signals enter the various layers of our atmosphere, and these miscalculations are only amplified when crossed radio transmissions of similar frequency closer to ground level. To avoid these inefficiencies, the PTC program will utilize the Nationwide Differential Global Positioning System (NDGPS), which consists of a network of ground-based reference stations to serve as a closer point of reference between the GPS tracking satellites and the receivers utilized by railway fleet tracking departments across the nation. The underlying concept behind PTC is that a train receives information about its location and where it can safely travel, a set of information known as movement authorities.  Onboard computers then take the GPS tracking data and control all movement operations of the train, preventing unsafe movement. Because of the intermittent use of ground-based reference stations, rail fleet tracking managers can bypass tunnels, poor weather conditions, and other obstructions to accurate GPS tracking information known by fleet tracking professionals as “dark territory”.

 

The first main PTC implementation method makes use of fixed signaling infrastructure such as coded track circuits and wireless transponders to communicate with a train’s onboard speed control system. The second utilizes wireless data radios spread along a given track to transmit this dynamic information.  While the fixed infrastructure of the first implementation has proven to stand up longer with less need for maintenance, both methods utilize GPS tracking information to allow fleet tracking departments to defend against train separation and collision avoidance, line speed enforcement, and rail worker wayside safety. While the technology continues to improve and the kinks are worked out in both tiers of implementation, by 2025 it is quite possible that our nation will never have to relive the disaster of the 2008 Metrolink collision.