Constraint Programming for Railway Optimization

Station capacity optimization and track renewal planning


OpenGOV: Constraint-Based Optimization of Track Occupation Diagrams

OpenGOV interface

Cosling supports SNCF Réseau in developing OpenGOV, a decision-support tool designed to optimize Track Occupation Diagrams (TOD). This tool helps assigning trains to appropriate platform tracks and allocating circulation routes that minimize operational conflicts. Station capacity optimization relies on a detailed modeling of railway traffic constraints (infrastructure, rolling stock, operational standards, crossings, schedules, etc.) and the ability to quickly generate optimized solutions.

OpenGOV uses advanced constraint programming algorithms developed by Cosling, based on Choco Solver. Routing thousands of trains is executed in just a few seconds, with proven optimality using a multi-objective function. By drastically reducing the number of conflicts, these technologies improve station circulation flow and enhance the robustness of railway operations.

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3 Tools

The OpenGOV suite includes three modules to support decision-making throughout the entire process:

  • OpenGOV Etudes: provides objective quantitative support for preliminary studies
  • OpenGOV Conception: optimizes transport plans from initial design to pre-operational adaptation
  • OpenGOV Temps-Réel: assists agents in managing real-time disruptions

+50 Stations

OpenGOV Design has been deployed in more than 50 stations across France. The solution is highly configurable to accommodate the various specificities of different stations (e.g., 2TMV), whether modeled at a macroscopic or microscopic level.

+30,000

Every day, our algorithms optimize over 30,000 train circulations. This leads to better infrastructure utilization, more robust track occupation diagrams, and ultimately, improved punctuality.


Track Occupation Diagram Optimization from Design to Pre-Operational Adaptation

Track Occupation Diagrams are at the core of railway network management. Leveraging the efficiency of Choco Solver, OpenGOV optimizes these diagrams from the design phase and dynamically adjusts them during pre-operational adaptation. The mathematical model integrates the deviation from the previous solution into the multi-objective function, ensuring minimal unnecessary changes and a seamless user experience. These models account for potential disruptions and anticipate conflicts, enabling smooth traffic adjustments in response to real-world uncertainties.




Constraint Programming for Operational Studies

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What would be the impact on traffic if a switch were removed? Can a specific maintenance operation start earlier? Is the planned transport increase feasible? Can we handle the upcoming Olympic Games? These questions require rigorous evaluation of structural decisions and comparison of multiple scenarios. Without proper tools, obtaining answers could take weeks, often leading to delays in decision-making. To address this challenge, Cosling developed OpenGOV Etudes for SNCF Réseau, a solution designed to facilitate operational studies.

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OpenGOV Etudes allows for station model modifications to simulate strategic changes instantly and assess their impact using constraint-based optimization algorithms. Whether the modification involves infrastructure, operations, transport plans, or maintenance work, OpenGOV Etudes reoptimizes the TOD by reallocating trains to available tracks and minimizing conflicts. The global optimization algorithm delivers results within minutes, thanks to the power of Constraint Programming and Choco Solver.




Optimization of Track Renewal Work Planning

Optimizing maintenance and track renewal is crucial to ensuring SNCF network performance. With strict constraints (maintenance windows, resource availability, disruption reduction) and operational requirements, planning becomes a complex challenge. Cosling supports SNCF by leveraging the power of Choco Solver and OR-Tools to generate intelligent schedules, maximizing work efficiency while minimizing impact on railway traffic. Thanks to this innovative approach, infrastructure management gains in reliability, fluidity, and precision.

Chantiers de renouvellement de voies



What Our Clients Say About Us

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Marion P.
Project Manager
SNCF Réseau
❝ Cosling has brought undeniable value to several optimization and operations research projects led by DGEX Solutions, particularly through the following key aspects:
  • - Genuine and demonstrated expertise in optimization and operations research
  • - Deep understanding of specific business challenges and the ability to develop tools closely aligned with real-world needs
  • - An efficient and scalable solver adaptable to encountered problems
  • - Autonomy and a proactive approach, offering innovative solutions or challenging client requirements when necessary to deliver a perfectly tailored tool
  • - Agile work methodology, assisting in refining client needs. ❞