Optimal Bus Scheduling Considering Operating Costs and Emissions: A Multiple Objective, Mixed Integer Programming Framework

Abstract

Traditional vehicle scheduling problems primarily focus on minimizing operating costs, and few of them consider the environmental impacts of the fleet operation. This study develops a framework that optimizes bus assignments to routes with the objective of minimizing both operating costs and the environmental impacts of emissions. The optimization model is applied in a case study of Metro Transit in Minneapolis/St Paul area. The results show a set of tradeoff relationships between operating costs and emissions. The optimized vehicle assignments generated by the model can significantly reduce both the operating costs and emissions of the current fleet. It is also found that hybrid electric buses were underused by Metro Transit in 2013 and should be assigned to service more often. The analysis can also provide useful supporting information for strategic decisions such as vehicle replacement and purchase.