Abstract
Urban buses usually require several distinct types of preventive maintenance. Due to the complexity of urban buses, quantifying the efficiency of preventive maintenance is very important for maintenance management decision-making and optimization. This study presents a sequential imperfect preventive maintenance model to quantify the maintenance efficiency of urban buses. Existing works of sequential imperfect preventive maintenance models are all formulated based on failure intensity reduction. The proposed model in this study defines maintenance efficiency as a proportion of the difference between actual and expected failure intensity increments. Since the proportion of the difference can vary from negative to positive, the proposed model can quantify all kinds of maintenance efficiency given in the existing works. A case study of an urban bus fleet in China is presented to illustrate the effectiveness of the model.