fa Electrical railway Electrical railway پژوهشي Research This study is concerned with the real-time delay recovery problem in metro loop lines. Metro is the backbone of public transportation system in large cities. A discrete event model for traffic system of metro loop lines is derived and presented. Two effective automatic controllers, linear quadratic regulator (LQR) and model predictive controller (MPC), are used to recover train delays. A newly-designed real-time algorithms for constrained LQR and constrained MPC in the presence of operational constraint on control actions is introduced. MPC and LQR automatic controllers are compared for traffic regulation in metro loop lines. To facilitate fair comparison of the performance of the automatic controllers, different scenarios are considered. The results are then compared to determine the relative effectiveness of the controllers. Constrained control, Linear quadratic regulator, Model predictive controller, Delay recovery, Metro loop line 23 31 http://ijrare.iust.ac.ir/browse.php?a_code=A-10-83-3&slc_lang=fa&sid=1 Sima Najafi 180031947532846001366 180031947532846001366 Yes School of Railway Engineering, Iran University of Science and Technology School of Railway Engineering, Iran University of Science and Technology Bijan Moaveni b_moaveni@iust.ac.ir 180031947532846001367 180031947532846001367 No School of Railway Engineering, Iran University of Science and Technology School of Railway Engineering, Iran University of Science and Technology