Empty vehicle traffic plays a critical role in the operating performance of automated guided vehicle systems (AGVSs). While significant research has been conducted on intelligent AGVS dispatching-which, in essence, is the management of empty vehicle traffic-research in AGVS design has sometimes ignored or simplified the role of empty vehicle traffic. In this paper, we show how empty vehicle traffic strongly influences several important AGVS design problems, such as flowpath design and vehicle requirements. We present analytical models to predict empty vehicle travel under two popular vehicle dispatching rules for systems facing stochastic trip demand. We show that using our models' estimates of empty vehicle traffic in the AGVS design process can dramatically improve the resulting system performance. We also analyse shop-floor transfer patters and find that empty traffic has a larger impact on systems with discernible trends in job movement.
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M. Eric Johnson (2001) studied this question.