Positive train control

Positive train control (PTC) is a system of functional requirements for monitoring and controlling train movements and is a type of train protection systems. The term stems from Control Engineering. The train is only allowed to move in case of positive movement allowance. It generally improves the safety of railway traffic.

Train protection systems are used to control traffic movement by technical means. They are especially needed in cases of high speed transportation, dense traffic with short succession of trains and mixed type traffic at wide differing speeds. So the train protection systems were in practical testing at least since the beginning of the 1930s in Europe.

For easy starting and high importent was the main task: Stopping a running train. This is most easily done with stop order. So without special order the vehicle is allowed to run. Typical representative for this technically termed negative train control is Indusi.

After declining of importance of railway transports in USA after WWII there was also slower requirement for investments in train security. At the end of the 1980s began the search for solutions together with an inventory of technical posibilities.

The main concept in PTC (as defined for North American Class I freight railroads) is that the train receives information about its location and where it is allowed to safely travel, also known as movement authorities. Equipment on board the train then enforces this, preventing unsafe movement. PTC systems may work in either dark territory or signaled territory, and may use GPS navigation to track train movements.

The Federal Railroad Administration (FRA) has listed among its goals, "To deploy the Nationwide Differential Global Positioning System (NDGPS) as a nationwide, uniform, and continuous positioning system, suitable for train control."

Various other benefits are sometimes associated with PTC such as increased fuel efficiency or locomotive diagnostics; these are benefits that can be achieved by having a wireless data system to transmit the information, whether it be for PTC or other applications.

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