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Thursday , February 22 , 2018


Rail system simulation for risk assessment, safety and operational analyses

A tool that simulates train movements with abilities to predict hazards and unsafe conditions, to facilitate risk assessment, safety and operational analyses.


Risk assessment with high degree of confidence

A principal challenge in introducing new railroad traffic control technology, like positive train control (PTC), is to demonstrate convincingly that safety will not be compromised. The Federal Railroad Administration (FRA) has established guidelines for submitting a performance-based Product Safety Plan (PSP), which is to include a risk assessment of potential accident scenarios. GTMS was developed for the FRA.


A key risk driver is the frequency with which events occur that may be precursors to hazardous situations leading to accidents. Such events may be the intersection of a train with a device or certain situations of train-to-train proximity. Reliable probability estimates of these events, or “exposure metrics”, can be derived through the simulation of a rail system, which realistically replicates both train movements and the system of traffic control.

Hazards, collisions and derailments are rare events whose probabilities of occurrence can be predicted through advanced simulation methods. GTMS is a proven tool that achieves this requirement.

DecisionTek Solution

Simulation Tool Predicts Probabilities of Railroad Hazards, Accidents and their Severity

GTMS (General Train Movement Simulator) supports the safety evaluation of plans for new products and systems related to Positive Train Control (PTC). Under continuing development by DecisionTek for the FRA, GTMS incorporates a precision train movement simulation capability, a system-wide traffic control simulation capability and supports safety analyses through the prediction of railroad hazards, accidents and their severity.

GTMS At-A-Glance

General Train Movement Simulator

GTMS simulates rail operations in support of risk assessments and safety and operational analyses. GTMS features include:

  • A train movement algorithm that calculates time, position, speed and the forces acting on a train.
  • A central dispatcher algorithm that prioritizes train movements; makes routing decisions; prevents train deadlock; and effects the safe separation of trains.
  • The tracking and reporting of exposure events of interest, namely: intersections of trains with track elements, and meets and passes of trains.
  • Modeling of causal chains leading to accidents and parameterization of factors affecting human errors and responses.
  • Rare event simulation and calculation of annual predicted accidents by type and the mean time to hazard (MTTH).
  • The ability to manage, share and manipulate data representing: a railroad’s physical plant; trains and their consists; and railroad operating schedules.
  • A system database that stores both input and results data, including time-speed-position of trains, and authorization status of traffic control blocks.
  • Simulation of railroad operations including: regular timetable operations; General Code of Operating Rules (GCOR) Forms A and B (speed restrictions); pick up and set out operations.
  • A set of tables and charts for reporting results and enabling the analysis of simulations.
  • Ability to simulate up to five years of railroad operations.

About GTMS

General Train Movement Simulator (GTMS) is a simulation-based software tool that evaluates the safety risk in a specific territory and makes before-and-after risk comparisons with PTC. Along with robust data management and reporting capabilities, GTMS features:

GTMS is the first full train movement simulator that fully integrates safety modeling with simulation of the railroad environment, enabling direct calculation of key safety risk metrics.
  • Train Performance Calculator – Time, speed and position are accurately replicated while accounting for resistive forces, locomotive power, braking forces, train handling, terrain and track geometry for representative trains according to forecast schedules.
  • Deadlock-free Traffic Control – The System Traffic Control Module replicates dispatcher authorizations according to schedules and priorities while managing railroad operations generally, including Forms A and B speed restrictions.
  • Safety Modeling – Human errors and responses along with equipment failures are permitted to occur in the system and then evolve to hazards, or safe resolution. Errors, failures and downstream outcomes are driven by user-specified error and failure rates and other factors. The evolution of unsafe conditions into hazards and accidents is reflective of best available information and the simulated railroad environment.
  • Staged Simulation – The bottom-line metrics of the evaluation (i.e., annual predicted accidents, mean time to hazard) are derived through an advanced simulation technique that parses the sample space to focus on paths of interest that lead to hazards and accidents. At each stage of the simulation, system states are captured and stored when events leading to accidents occur. In subsequent stages, these previous states are sampled and re-animated and further simulated until a successive event of interest or safe resolution is achieved. The staged simulation permits a straight-forward calculation of metrics of interest and the system enables second-by-second tracking of simulated accidents.

GTMS also offers user-friendly interfaces for uploading, downloading and sharing data. The software readily accommodates the development of multiple simulation scenarios.

GTMS can be useful in several stages in the lifecycle deployment of PTC:

  • Design –While engineering analyses can test systems on a component-by-component basis, GTMS can test a deployed design concept. The system can support design by testing assumptions and identifying flaws in a simulated railroad environment that accounts for human errors, human responses and system operations.
  • Validation – GTMS can validate a completed PTC system to determine that it indeed delivers the planned level of safety.
  • Assessment – For non-vital overlay systems GTMS can perform the risk assessment required by the PTC Rule.
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