Overview

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 60,000 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: 

• Train-to-train collisions;
• Overspeed derailments;
• Incursion into an established work zone; and
• Movement through a main line switch in the improper position.
• Other functions are applicable within the requirements as specific conditions warrant.

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.

Types of PTC Systems in the United States 

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.)

ACSES II: The latest version of Advanced Civil Speed Enforcement System, and acts as a vital overlay to an Automatic Train Control (ATC) system comprised of a Cab Signaling System (CSS) and a Speed Control System (SCS). (Type Approved and Certified by FRA.)

• ACSES II Type Approval here
• SEPTA implementation, Variances 1,2, and 3 Type Approval here
• ASES II Type Approval here
• ACSES II (Non-ATC) Type Approval here

CBTC (Communications-Based Train Control): A vital stand-alone Positive Train Control (PTC) system, as defined in 49 Code of Federal Regulations (CFR) Part 236, Subpart I, Section 236.1015(e)(3). CBTC replaces the existing traffic control method of operation by requesting an override of the wayside signal system to display a Flashing Green or Flashing Yellow (if the green aspect does not illuminate) signal aspect. (Type Approved and Certified by FRA.)

• CBTC Type Approval here

ETMS (Electronic Train Management System): A GPS- and communications-based system previously 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.)

• ETMS Type Approval here

I-ETMS (formerly called Vital Electronic Train Management System): A GPS- and communications-based system ready for deployment. It is the system of choice for CSX Transportation, Norfolk Southern Railway, Union Pacific Railroad and BNSF Railway. Various passenger/commuter and other railroads are adopting it for compatibility and interoperability. (Type Approved by FRA.)

• I-ETMS Type Approval here

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.

• ITCS Type Approval here

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.

• E-ATC Type Approval here

I-ITCS (Interoperable Incremental Train Control System): A safety-critical, overlay system as defined in 49 CFR Part 236, Subpart I, Section 236.10 15(e), to be used in conjunction with the existing method of operation (Traffic Control System). I-ITCS interoperability is achieved by incorporating the same capabilities as the Interoperable Electronic Train Management System (I-ETMS). (Type Approved by FRA.)

• I-ITCS Type Approval here

SafeNet System: The Argenia Railway Technologies’ Positive Train Control (PTC) system (SafeNet System) is a non-vital overlay PTC system, as defined in 49 CFR § 236.1015 (e)(1). The SafeNet System is designed to support the Nashville & Eastern Railroad (NERR) and its method of operation. The SafeNet System will be used in conjunction with the existing method of operation, centralized traffic control (CTC), which interfaces with existing signal systems, wayside devices, and office train dispatching systems Computer-Aided Dispatch (CAD) via multiple communications links. (Type Approved by FRA.)

• SafeNet Type Approval here

Sentinel System: An overlay Positive Train Control (PTC) system, as defined in Title 49 Code of Federal Regulations (CFR) Part 236, Subpart I, Section 236.l 015( e )(1 )(ii). This CBTC system is overlaid on the existing method of operation and provides enforcement of movement authority limits, maximum authorized speeds, permanent and temporary speed restrictions, and incursion into roadway work zones by a positive stop. (Type Approved and Certified by FRA.)

• Sentinel Type Approval here

Regulations

(Title 49 CFR)

• Part 229--Railroad Locomotive Safety Standards
• Part 234—Grade Crossing Safety, Including Signal Systems, State Action Plans, And Emergency Notification Systems
• Part 235—Instructions Governing Applications For Approval Of A Discontinuance Or Material Modification Of A Signal System Or Relief From The Requirements Of Part 236
• Part 236—Rules, Standards, And Instructions Governing The Installation, Inspection, Maintenance, And Repair Of Signal And Train Control Systems, Devices, And Appliances