Bernardo Martin-Iradi


Last Name

Martin-Iradi

First Name

Bernardo

ORCID

0000-0003-0046-2531

Organisational unit

09611 - Corman, Francesco / Corman, Francesco

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2022 - 202516
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Publications 1 - 10 of 16
  • Handling conflicts in microscopic railway timetabling at scale
    Item type: Working Paper
    Fuchs, Florian; Dubach, Thomas; Lordieck, Jan; et al. (2025)
    SSRN
    This paper presents a hybrid optimization framework for microscopic railway timetabling that integrates Logic-Based Benders Decomposition with Conflict Discovery (CD-LBBD) and a Soft-Conflict Mixed-Integer Programming (SC-MIP) formulation. The CD-LBBD method separates high-level coordination from microscopic feasibility, employing an SMT-based subproblem to dynamically detect and resolve resource conflicts. The SC-MIP formulation, by contrast, introduces a continuous relaxation of disjunctive precedence constraints and iteratively minimizes conflict violations to obtain feasible schedules that are subsequently refined to optimality. Both approaches operate on a strengthened continuous-time event–activity formulation enhanced by bound propagation, structural clustering, traversal bounds, and resource aggregation into train-specific chunks.The proposed framework is evaluated on the complete DISPLIB~2025 benchmark set, comprising 112 real-world–based instances. Within a 10-minute competition limit, CD-LBBD and SC-MIP jointly solved 65 instances to optimality. The hybrid solver achieves 91 best-known solutions—approximately 81\% of the benchmark—and obtained the highest overall score in the DISPLIB~2025 competition. These results demonstrate that combining exact methods with complementary algorithmic structures provides robust and scalable performance for large-scale, microscopic railway timetabling.
  • DISPLIB competition
    Item type: Conference Poster
    Dubach, Thomas; Fuchs, Florian; Lordieck, Jan; et al. (2025)
    DISPLIB 2025 challenged participants to advance real-time railway scheduling. We present a hybrid approach: Logic-based Benders decomposition dynamically discovers and separates train conflicts, while an incremental MIP relaxes constraints and iteratively converges to optimal solutions. This dual strategy maintains tractability while providing optimality guarantees.
  • Optimizing periodic stability in railway timetables: A microscopic model for networks with a macroscopic comparison
    Item type: Journal Article
    Fuchs, Florian; Martin-Iradi , Bernardo; Corman , Francesco; et al. (2025)
    Journal of Rail Transport Planning & Management
    We present a novel microscopic model for railway timetabling designed to maximize periodic stability in mixed single- and multi-track networks. Unlike conventional approaches based on the Periodic Event Scheduling Problem (PESP), our model provides a detailed infrastructure representation with flexible routing and nuanced conflict resolution, enhancing adaptability to real-world constraints and facilitating practical implementation by operators. To ensure scalability, we integrate a Satisfiability Modulo Theories (SMT)-based approach, which efficiently narrows feasible cycle time bounds, enabling the model to handle large-scale networks. Validated on operational data from the Rhätische Bahn network—a Swiss railway with complex infrastructure—the microscopic model consistently yields lower minimal cycle times than its macroscopic counterpart. The comparative analysis also offers insights into the trade-offs between model detail, computational efficiency, and achievable cycle times across diverse operational scenarios. These findings underscore the importance of infrastructure abstraction and the careful consideration of operational and commercial interdependencies for optimal stability in complex railway networks.
  • An adaptive large neighborhood search heuristic for the multi-port continuous berth allocation problem
    Item type: Working Paper
    Martin-Iradi, Bernardo; Pacino, Dario; Ropke, Stefan (2023)
    arXiv
    In this paper, we study a problem that integrates the vessel scheduling problem with the berth allocation into a collaborative problem denoted as the multi-port continuous berth allocation problem (MCBAP). This problem optimizes the berth allocation of a set of ships simultaneously in multiple ports while also considering the sailing speed of ships between ports. Due to the highly combinatorial character of the problem, exact methods struggle to scale to large-size instances, which points to exploring heuristic methods. We present a mixed-integer problem formulation for the MCBAP and introduce an adaptive large neighborhood search (ALNS) algorithm enhanced with a local search procedure to solve it. The computational results highlight the method's suitability for larger instances by providing high-quality solutions in short computational times. Practical insights indicate that the carriers' and terminal operators' operational costs are impacted in different ways by fuel prices, external ships at port, and the modeling of a continuous quay.
  • Capacity planning for demand-responsive multimodal transit
    Item type: Presentation
    Martin-Iradi, Bernardo; Corman, Francesco; Geroliminis, Nikolas (2024)
  • A column-generation-based matheuristic for periodic and symmetric train timetabling with integrated passenger routing
    Item type: Journal Article
    Martin-Iradi, Bernardo; Ropke, Stefan (2022)
    European Journal of Operational Research
    In this study, the periodic train timetabling problem is formulated using a time-space graph formulation that exploits the properties of a symmetric timetable. Three solution methods are proposed and compared where solutions are built by what we define as a dive-and-cut-and-price procedure. An LP relaxed version of the problem with a subset of constraints is solved using column generation where each column corresponds to the train paths of a line. Violated constraints are added by separation and a heuristic process is applied to help to find integer solutions. The passenger travel time is computed based on a solution timetable and Benders’ optimality cuts are generated allowing the method to integrate the routing of the passengers. We propose two large neighborhood search methods where the solution is iteratively destroyed and repaired into a new one and one random iterative method. The problem is tested on the morning rush hour period of the Regional and InterCity train network of Zealand, Denmark. The solution approaches show robust performance in a variety of scenarios, being able to find good quality solutions in terms of travel time and path length relatively fast. The inclusion of the proposed Benders’ cuts provide stronger relaxations to the problem. In addition, the graph formulation covers different real-life constraints and has the potential to easily be extended to accommodate more constraints.
  • The Multiport Berth Allocation Problem with Speed Optimization: Exact Methods and a Cooperative Game Analysis
    Item type: Journal Article
    Martin-Iradi, Bernardo; Pacino, Dario; Ropke, Stefan (2022)
    Transportation Science
    We consider a variant of the berth allocation problem—that is, the multiport berth allocation problem—aimed at assigning berthing times and positions to vessels in container terminals. This variant involves optimizing vessel travel speeds between multiple ports, thereby exploiting the potentials of a collaboration between carriers (shipping lines) and terminal operators. Using a graph representation of the problem, we reformulate an existing mixed-integer problem into a generalized set partitioning problem, in which each variable refers to a sequence of feasible berths in the ports that the vessel visits. By integrating column generation and cut separation in a branch-and-cut-and-price procedure, our proposed method is able to outperform commercial solvers in a set of benchmark instances and adapt better to larger instances. In addition, we apply cooperative game theory methods to efficiently distribute the savings resulting from a potential collaboration and show that both carriers and terminal operators would benefit from collaborating.
  • The Multi-port Continuous Berth Allocation Problem with Speed Optimization
    Item type: Conference Paper
    Martin-Iradi, Bernardo; Pacino, Dario; Ropke, Stefan (2022)
    Lecture Notes in Computer Science ~ Computational Logistics
    We study the multi-port continuous berth allocation problem with speed optimization. This problem integrates vessel scheduling with berth allocation at multiple terminals in a collaborative setting. We propose a graph-based formulation and a branch-and-price method to solve the problem. The results show that the branch-and-price procedure outperforms the baseline solver. In our computational study, we highlight the trade-off between solution quality and computational complexity, as a function of the segment length used to model a continuous quay.
  • Dynamic capacity planning for demand-responsive multimodal transit
    Item type: Conference Paper
    Martin-Iradi, Bernardo; Corman, Francesco; Geroliminis, Nikolas (2024)
    Demand-responsive multimodal transit offers opportunities to complement existing public transport systems and provide an overall better service level to passengers while at the same time making better use of the resources. This study optimizes the capacity of such system by strategically sizing the required fleet and allocating it to the operating services. We formulate a two-stage stochastic optimization model that plans the transit system and the required fleet in the first stage, and optimizes the demand-responsive operations in the second stage. We develop a decomposition-based method that exploits the network-based formulation of the second stage, allowing us to solve practical instances. Preliminary results from a case study in the city of Zurich show that designing a public transport system together with demand-responsive mobility systems can benefit both transport operators and passengers. By allocating the system capacity more efficiently, operators reduce operational costs while maintaining or improving the travel experience for passengers.
  • Coordinating partially periodic railway timetables across scenarios using logic-based benders decomposition
    Item type: Other Conference Item
    Fuchs, Florian; Dubach, Thomas; Corman, Francesco; et al. (2025)
    ODS 2025 Book of Abstract
    Strategic railway timetables are typically designed years in advance to define a stable and memorable passenger-oriented offer. However, transforming these long-term plans into operationally feasible daily schedules requires adapting to real-world fluctuations in demand, rolling stock availability, freight services, and infrastructure works. Despite such day-to-day variability, passengers expect consistent departure and arrival times. This creates a coordination challenge: trains recurring across operational days must comply with a shared commercial schedule, never departing earlier nor arriving later than publicly announced. We present a scalable optimization framework to address this challenge at the microscopic level. Our approach extends a Logic-Based Benders Decomposition (LBBD) scheme to jointly optimize train order, routing, and timing across multiple daily scenarios. It supports both periodic and non-periodic services while enforcing cross-scenario consistency on commercial train events. As the number of scenarios and periodic replications grows, the complexity increases rapidly. To ensure tractability without compromising solution quality, we introduce an effective conflict pruning procedure that reduces constraints by over 95%. Using real data from the Rhätische Bahn (RhB) network, we benchmark three planning strategies: synchronized, independent, and sequential. The direct MIP formulation struggles to solve non-trivial instances due to weak scaling and numerical instability. In contrast, our LBBD-based method, enhanced by fast branching and conflict aggregation, consistently produces feasible, synchronized timetables with moderate overhead. The proposed approach is implemented in the openBus optimization toolbox, enabling practitioners to transform long-term strategic plans into consistent and operationally viable daily timetables.
Publications 1 - 10 of 16