Strategic Vehicle Fleet Management - The Composition Problem

Abstract

Background: Fleets constitute the most important production me ans in transportation. Their appropriate management is crucial for all companies having tran sportation duties. The paper is the second one of a series of three papers that the author dedicates to the strategic v ehicle fleet management topic. Material and methods: The paper discusses ways of building companies' fl eets of vehicles. It means deciding on the number of vehicles in a fleet (the fleet sizing problem - FS) and types of vehicles in a fleet (th e fleet composition problem - FC). The essence of both problems lies in balancing transportation supply and demand taking i nto account different demand types to be fulfilled and differen t vehicle types that can be put into a fleet. Vehic les, which can substitute each other while fulfilling different de mand types. In the paper an original mathematical model (an optimization method) allowing for the FS/FC anal ysis is proposed. Results: An application of the proposed optimization method in a real-life decision situation (the case study) within the Polish environment and the obtained solution ar e presented. The solution shows that there exist so me best fitted (optimal) fleet size / composition matching company's transportation requirements. An optimal fleet si ze / composition allows for a significantly higher fleet utilization (10-15% higher) than any other, including random f leet structure. Moreover, any changes in the optimal fleet size / c omposition, even small ones, result in a lower util ization of vehicles (lower by a few percent). Conclusions: The presented in this paper analysis, on the one h and, is consistent with a widespread opinion that t he number of vehicle types in a fleet should be limite d. In the other words it means that the versatility / interchangeability of vehicles is very important. On the other hand, the analysis proves that even small changes in a fleet size / fleet composition can result in an important changes of t he fleet effectiveness (measured for example by the utilization ratio).