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Policy Issues


Positive Train Control

AAR POLICY POSITIONFreight railroads support the development and implementation of PTC.

Positive Train Control (PTC) is a set of highly advanced technologies designed to make freight rail transportation — already one of the safest U.S. industries — even safer by automatically stopping a train before certain types of accidents occur.

Class I railroads are on track to meet all statutory deadlines to install and implement PTC. 

In the years to come, freight railroads will continue to safely deploy all necessary equipment and outfit the locomotive fleet with PTC technology. The rail industry will also conduct thorough testing and validation to ensure that the system works, before this groundbreaking and technologically-complex system is operationalized across the freight rail network. 


The Rail Safety Improvement Act of 2008 originally called for passenger railroads and class I freight railroads to install PTC by the end of 2015 on main lines used to transport passengers or toxic-by-inhalation (TIH) materials. In October 2015, the statutory deadline for PTC installation was extended to the end of 2018, with further extensions ava​ilable up to the end of 2020 to allow time for railroads to adequately test their systems. The 2018 deadline requires that all of the hardware and software must be installed and at least 50% of the route miles must be operable.

A further extension to 2020 is available should railroads meet that requirement to allow adequate time to test and ensure that the system works as Congress intended.  


As mandated by law, PTC will:

  • Prevent train-to-train collisions.
  • Derailments caused by excessive speed.
  • Unauthorized incursions by trains onto sections of track where maintenance activities are taking place.
  • Movement of a train through a track switch left in the wrong positions.

PTC will not prevent:

  • Accidents caused as a result of track equipment failure.
  • Improper vehicular movement through a grade crossing.
  • Trespassing on railroad tracks.
  • Certain types of train operator error.


The sophisticated and complicated PTC technology must account for a number of factors to measure the appropriate train stopping distance, including train information (weight, length); track composition (curvature, terrain); train speed and train authority (authorization to move across a stretch of track).

There are three main elements of a PTC system, which are integrated by a wireless communications system:

1. Onboard or Locomotive System: Monitors the train’s position and speed and activates braking as necessary to enforce speed restrictions and unauthorized train movement into new sections of track.

2. Wayside System: Monitors railroad track signals, switches and track circuits to communicate authorization for movement to the locomotive.

3. Back Office Server: The storehouse for all information related to the rail network and trains operating across it — speed limits, track composition, speed of individual locomotives, train composition, etc.— and transmits the authorization for individual trains to move into new segments​ of track.


  • Developing PTC Technology: Much of the technology PTC requires did not exist when the mandate became law in 2008. Railroads had to develop the required technology for locomotives, wayside interface units and back office systems from scratch. Once developed, each element must undergo rigorous testing before it can be deployed. Railroads have also been challenged by the limited number of firms that provide technical design services, particularly for signal systems, many of which have to be redesigned before PTC technology can be installed.

  • Deploying hundreds of thousands of technology pieces: PTC involves the deployment of hundreds of thousands of technology pieces—from onboard locomotive systems to switch position monitor—across the nationwide rail network.

  • Geo-mapping 60,000 miles: The approximately 60,000 miles of railroad right-of-way on which PTC technology will be installed and 486,000 field assets (i.e. mileposts, curves, grade crossings, switches, signals, etc.) must be precisely geo-mapped for PTC technology to work correctly. This mapping forms the basis for the system’s track database used by the back office server.

  • Interoperability is essential: To function properly, PTC systems must be interoperable so that any train operating on another railroad’s network can communicate with the host railroad’s PTC system. 

  • Equipping 1,900 “dark territory” switches with power: Some long stretches of track in remote areas use only one main line without any signalization. To make these areas PTC compatible, railroad switches must be upgraded and electrical power must be brought to the site.

  • Phased rollout is critical for safety: Implementation of PTC must occur in phases and location by location, starting with less complex areas and proceeding to the more operationally complex areas with lessons learned incorporated at each step to ensure that the system functions safely. Rushing PTC development and installation and foregoing a logical plan for sequencing its implementation would sharply increase the likelihood that the system would not work as it should.

  • Required testing software is not available: Once all testing of individual PTC components is complete and those components have been installed, testing of the entire system as a whole can begin.

  • Training cannot be completed until the PTC system is operational: PTC requires rigorous training for 125,000 Class I railroad and commuter rail employees, which will be completed in parallel with installation and deployment. Training will happen before the system is turned on.