Improved Squeaky Wheel Optimisation for Driver Scheduling 191

Abstract. This paper presents a technique called Improved Squeaky Wheel Op-timisation (ISWO) for driver scheduling problems. It improves the original Squeaky Wheel Optimisation’s (SWO) effectiveness and execution speed by incorporating two additional steps of Selection and Mutation which implement evolution within a single solution. In the ISWO, a cycle of Analysis-Selection-Mutation-Prioritization-Construction continues until stopping conditions are reached. The Analysis step first computes the fitness of a current solution to identify troublesome components. The Selection step then discards these trou-blesome components probabilistically by using the fitness measure, and the Mu-tation step follows to further discard a small number of components at random. After the above steps, an input solution becomes partial and thus the resulting partial solution needs to be repaired. The repair is carried out by using the Pri-oritization step to first produce priorities that determine an order by which the following Construction step then schedules the remaining components. There-fore, the optimisation in the ISWO is achieved by solution disruption, iterative improvement and an iterative constructive repair process performed. Encourag-ing experimental results are reported.