Elevator service time distribution for the product allocation problem in a multi-level distribution center

In a multi-level distribution center, elevator traffic operations during the down pattern are necessary to be considered when product allocation decision is made. In this paper, we take elevator service system in this situation as a serial correlated queuing system with one queue at every floor. For these queue systems, we first redefine service time of every queuing system. Then we divide the service time into two independent parts and derive distributions of these two parts respectively in a recursive way. With the convolution technique we obtain the service time distribution of every queuing system. Sample numerical example is presented at the end.