Reducing Truck Emissions in Import Operations at Container Terminal—A Case Study in a Singaporean Port - Technology Management for Sustainable Production and Logistics - page 140

12 345 12 345…1 23 45

1 0 1 1 1 1 1 0 0 1…0 0 1 1 1

Container 1 Container 2 Container I

Fig. 2 Structure of a chromosome

4.2 Simulation Model

Figure 3 shows the simulation process as following. In order to calculate the
objective function, simulation is used to find E ( X ), the average total waiting time
of trucks picking up containers. As mentioned above, there is a probability for the
selection of arrival time of trucks and the probability density function is given.
Hence, for each container, the arrival time of the truck picking up that container is
determined based on the given available periods and the probability density func-
tion of selection. If we use p it to denote the selected period for picking up con-
tainer i , it will satisfy the following constraints. These two equations ensure that a
container will be picked only once and only during the available periods.

T

p it = 1 ∀ i ∈ { 1, ... , I }

(5)

t = 1

T

p it x it = 1 ∀ i ∈ { 1, ... , I }

(6)

t = 1

Fig. 3 The process of the
simulation model

Input: X it

Simulate truckers' selection behavior on arrival periods

Randomly generate truck arrival time in each period

Simulate gate operations

Simulate yard operations