Techniques for restricting multiple overtaking conflicts and performing compound moves when constructing new train schedules

In this paper a discrete sequencing approach for train scheduling is extended firstly by incorporating essential composite perturbation operations and secondly by restricting unnecessary multiple overtaking. Unnecessary multiple overtaking occurs when a train overtakes another train using a siding but is itself overtaken at a later time on a different siding by the train that it previously passed. Compound perturbation operations may be needed in order to restrict precedence impossibilities from occurring when passing facilities do not separate adjacent sections of rail since the sequences are linked by common precedences. Both features affect the sequencing process and can significantly improve the solution quality if handled efficiently and correctly. From a numerical investigation significant benefits are demonstrated on benchmark problems of a previous paper.