Publications

2017

• Optimization and simulation for robust railway rolling-stock planning
  
  • Tréfond Sabine
  • Billionnet Alain
  • Elloumi Sourour
  • Djellab H.
  • Guyon Olivier
  Journal of Rail Transport Planning & Management, 2017. In this paper, we focus on the problem of robust rolling-stock planning for French passenger trains. First, we characterize robustness and define some indicators for the evaluation of rolling-stock rosters. We take a particular interest in homogenizing turning-times in a roster in order to absorb potential delays. Then, we propose a new approach to solve the problem of robust rolling-stock planning. The SNCF reference tool (PRESTO) calculates a solution to the rolling-stock planning problem. It consists of a multi-step approach to cover demand while minimizing operating costs, and to further add maintenance slots to the roster. We propose an integrated ILP model to add robustness to a roster while maintaining low operating costs compared to PRESTO. We have carried out tests on nine real French regional transport instances, and we use a simulation module to evaluate the results. We observe a significant improvement in robustness indicators while maintaining low operating costs and meeting maintenance requirements. (10.1016/j.jrtpm.2017.02.001)
  DOI : 10.1016/j.jrtpm.2017.02.001
• The Mayer and Minimum Time Problems with Stratified State Constraints *
  
  • Hermosilla C.
  • Wolenski P.R.
  • Zidani Hasnaa
  Set-Valued and Variational Analysis, Springer, 2017. This paper studies optimal control problems with state constraints by imposing structural assumptions on the constraint domain coupled with a tangential restriction with the dynamics. These assumptions replace pointing or controllability assumptions that are common in the literature, and provide a framework under which feasible boundary trajectories can be analyzed directly. The value functions associated with the state constrained Mayer and minimal time problems are characterized as solutions to a pair of Hamilton-Jacobi inequalities with appropriate boundary conditions. The novel feature of these inequalities lies in the choice of the Hamiltonian. (10.1007/s11228-017-0413-z)
  DOI : 10.1007/s11228-017-0413-z