Technical Reports

Development of an Operationally Efficient PTC Braking Enforcement Algorithm for Freight Trains

  • 02
  • Aug
  • 2013
AUTHOR: Joe Brosseau, Bill Moore Ede, Shad Pate, RB Wiley, and Joe Drapa
OFFICE: RPD
REPORT NUMBER: DOT/FRA/ORD-13/34
SUBJECT: Positive Train Control
KEYWORDS: Braking algorithm, enforcement algorithm, positive train control, PTC, train control, simulation, Monte Carlo simulation, adaptive enforcement algorithm, emergency brake backup
ABSTRACT: Software algorithms used in positive train control (PTC) systems designed to predict freight train stopping distance and enforce a penalty brake application have been shown to be overly conservative, which can lead to operational inefficiencies by interfering with normal train operations. Federal Railroad Administration contracted Transportation Technology Center, Inc. to investigate approaches to improve these algorithms and to reduce the associated operational inefficiencies. As part of this program, several new approaches to PTC enforcement were introduced and were shown, through simulations and field testing, to improve the operational efficiency of the algorithm. An appropriate safety objective for these algorithms was established from a fault-tree analysis of the accidents PTC was conceived to prevent. A standard methodology was also established by which any PTC enforcement algorithm can be evaluated against design safety and performance measures. This methodology involves a statistical evaluation of the algorithm by means of a Monte Carlo simulation process, as well as limited, focused field testing, which provides more confidence in the safety and performance of the software at less cost than traditional field testing methods. This methodology was then used to evaluate PTC supplier algorithms that incorporate concepts introduced in this project.

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