Positive Train Control (PTC) is a processor-based/communication-based train control system designed to prevent train accidents. PTC may be voluntarily developed and implemented by a railroad following the requirements of Title 49 Code of Federal Regulations (CFR) Part 236, Subpart H – Standards for Processor-Based Signal and Train Control Systems; or, may be as mandated by the Rail Safety Improvement Act of 2008 developed and implemented by a railroad following the requirements of 49 CFR Part 236, Subpart I – Positive Train Control Systems.
With limited exceptions and exclusions as described within Subpart I potentially available, PTC is required to be installed and implemented on Class I railroad main lines (i.e., lines with over 5 million gross tons annually) over which any poisonous- or toxic-by-inhalation (PIH/TIH) hazardous materials are transported; and, on any railroad’s main lines over which regularly scheduled passenger intercity or commuter operations are conducted. It is currently estimated this will equate to approximately 70,000 miles of track and will involve approximately 20,000 locomotives.
PTC technology is capable of automatically controlling train speeds and movements should a train operator fail to take appropriate action for the conditions at hand. For example, PTC can enforce a train to a stop before it passes a signal displaying a stop indication, or before diverging on a switch improperly lined, thereby averting a potential collision. PTC systems required to comply with the requirements of Subpart I must reliably and functionally prevent:
PTC systems must also provide for interoperability in a manner that allows for equipped locomotives traversing other railroad’s PTC-equipped territories to communicate with and respond to that railroad’s PTC system, including uninterrupted movements over property boundaries.
ACSES (Advanced Civil Speed Enforcement System): A transponder-based system, in use on Amtrak's Northeast Corridor originally put into use on the Northeast Corridor by the specific requirements of an Order of Particular Applicability. (Type Approved and Certified by FRA.)
ETMS (Electronic Train Management System): A GPS- and communications-based system being deployed by BNSF Railway, originally put into use by the specific requirements of 49 CFR Part 236, Subpart H. (Type Approved and Certified by FRA for restricted use.)
I-ETMS (formerly called Vital Electronic Train Management System): A GPS- and communications-based system, not yet ready for deployment. It is the system of choice for CSX Transportation, Norfolk Southern Railway, and Union Pacific Railroad. BNSF Railway is to upgrade to it when software is available, various passenger/commuter and other railroads are adopting it for compatibility and interoperability. (Type Approved by FRA.)
ITCS (Incremental Train Control System): A GPS- and communications-based system used by Amtrak on its Michigan line, authorized for passenger train speeds up to 110 mph, originally put into use by the specific requirements of an FRA-approved waiver. ITCS certification through Amtrak's request for expedited certification process is pending successful resolution of a few remaining issues prior to FRA approval for certification.
E-ATC (Enhanced Automatic Train Control): A system that uses an underlying automatic train control (ATC) system, in conjunction with other “enhanced” features or systems to achieve the core required functionalities of PTC. These systems are often integrated with underlying cab signal systems (CSS) and centralized traffic control (CTC) systems, in addition to other signal or train control system enhancements the railroad elects to make, to meet the full requirements of PTC.