Optimisation of schedules for the inspection of railway tracks

Inspection of railway tracks involves a high volume of short-duration tasks (e.g. visual inspection, vehicle-based inspection, measurement, etc.) each of which is repeated at different frequencies and time intervals. It is important to gain as many benefits as possible from the inspection tasks, which incur huge expenses. To date, various optimisation methods have been incorporated into the schedule generation to determine an inspection order for a known number and geographical location of tracks. Due to the specific requirements of certain tracks or inspection problemfor example, the number of schedule parameters and one-off or incremental type schedulesresearchers have developed more sophisticated and problem-dependent optimisation methods. However, introduction of a new inspection technology and policy in the last five years, especially in the United Kingdom, has urged a remodelling of the scheduling problem in track inspection in order to cope up with the new operational and business constraints. Thus, this paper conducts a review and gap analysis of previous studies with regard to track inspection scheduling problems from an optimisation point of view. In addition, the authors discuss several potential research interests resulting from the gap analysis undertaken. This study shows that heuristic methods are popular among researchers in searching for an optimal schedule subject to single or multiple optimisation function(s) while satisfying various technical and business constraints.