Positive Train Control at the Trinity Railway Express

The Trinity Railway Express (TRE) maintains an excellent safety record since its opening in December 1996. Part of the reason is the ongoing efforts of its owners, Dallas Area Rapid Transit and Trinity Metro, to make safety the top priority. The implementation of Positive Train Control (PTC) is part of that effort.


What is PTC?

PTC is a set of advanced integrated technologies designed to automatically stop trains before certain accidents can occur. As part of the Rail Safety Improvement Act (RSIA) of 2008, this new technology is intended to prevent these four specific types of accidents:


  • Train-to-train collisions
  • Derailments caused by excessive train speed
  • Incursions into established work zone limits, without receiving appropriate authority
  • Movement of a train through a switch left in the improper position


How Does PTC Work?

PTC systems utilize real-time data collection and measurement of multiple changing factors that determine the appropriate distance for stopping each train. These measures include the train’s weight, length and speed, track composition factors including terrain and curvature, and train authority.


  • The onboard computer system in each train receives and analyzes data from GPS satellites, fiber-optic wayside locations and base-station radios along the planned route.
  • The back-office systems track millions of encrypted rail network data points and transmit the authorization for individual trains to move into new track segments.
  • PTC provides each train operator with advanced warning of speed limits, movement authority, and track conditions ahead, giving the operator time to react and bring the train to a safe speed or controlled stop.
  • If corrective action is not detected within the warning period, PTC automatically applies the train brakes and brings it to a controlled stop without the operator’s assistance.


TRE manages its corridor between Dallas and Fort Worth, determining when other rail operators can use it. This is an important part of keeping TRE safe.


However, the TRE PTC system must be fully interoperable with the PTC systems of five separate  railroads that have access to the TRE corridor. It is vital that different passenger, commuter and freight systems have seamless communication across the railroad system. Since the passage of RSIA, the rail industry has  beenworking to address interoperability.

This video ( https://youtu.be/UIXiwmZW0Yo) from the Association of American Railroads shows how PTC works.


Trinity Railway Express PTC Implementation

TRE is making significant progress in the installation of PTC. In April 2018, TRE submitted a test request to the FRA and received approval in May 2018. TRE has completed the following PTC required tests:

  • Critical Feature Validation and Verification – September 2018
  • F59PH and Bombardier Cab Car Brake Test – September 2018
  • Route Navigation and Speed Verification Test – September 2018
  • Wayside Interface Unit (WIU) Field Validation and Verification – October 2018


Status of Trinity Railway Express PTC Implementation

The status of TRE PTC installation as of Oct. 8, 2019.

  • All TRE locomotives and cab cars have been fully equipped and are PTC operable.
  • All TRE track segments are completed and PTC-compliant.
  • All required radio towers are installed, but not yet operable.
  • Required PTC spectrum is available and ready for use.
  • All wayside hardware has been installed.
  • 100% percent of training has been completed.

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