Design of passengers' circulation areas at the transfer station: An automated hybrid simulation-differential evolution framework

The capacity design of passengers' circulation areas at the transfer stations is a crucial issue from the designers' point of view. An adequate design reflects the better performance while inadequacy leads to the congestion issues at the transfer stations. To overcome the shortcomings in the design guide (TCRP-165 Report) and existing exponential-based (M/G(n)/N/N) design model, this paper reports a novel Discrete-Event Simulation (DES) model based on the Phase-Type (PH)-distributed random variates for the circulation areas (passageways and stairways), integrated with the Differential Evolution (DE) optimization approach. This hybrid simulation-optimization model is an automated framework that simultaneously works to provide optimal widths of the passengers' circulation areas, under a desirable Level-of-Service (LOS) and blocking probability criteria. The passengers' arrival and service time pattern of the circulation areas in the DES model is described by the PH distribution, which accurately takes into account the variation of passengers' arrival at different instants as well as randomness and state-dependent service time of the circulation areas. The comparison of proposed model with exponential-based (M/G(n)/N/N) model and TCRP-165 Report reveals that: (1) the optimal widths of circulation areas obtained by proposed model are greater than both M/G(n)/N/N and TCRP-100 Report; (2) the optimal width increases with the increase in squared coefficient of variation for all the passengers' arrival rates, LOS and lengths of the circulation areas; (3) the optimal width values drop from LOS B towards D; (4) our proposed simulation-DE optimization outperforms the simulation-GA optimization approach in term of the speed of convergence. This novel hybrid simulation-DE optimization framework is an effective tool for the designers of transfer stations in decision making process and analyzing the complex facilities with ease.