Information Technology Reference
In-Depth Information
import
provide
D
H
E
F
I
J
K
A
C
storage
B
G
export
customer
seaside
container
depots
terminals
locations
Fig. 1. Container flow in the hinterland of a seaport
transport requests. The vehicles are located at a single vehicle depot. We assume
that it is possible to transport at most two containers - either two 20-foot contain-
ers or one 40-foot container - at the same time with a single vehicle. We consider
a vehicle as a single entity, i.e., there are no trucks with trailers. However, we as-
sume that a container can be unloaded from a truck at each node of the hinterland
network.
There are four types of transport requests (cf. Fig. 1) which are characterized
from the point of view of a customer: (i) export requests, (ii) import requests,
(iii) storage requests, and (iv) provide requests. Each request r is determined by
atriple( r + ,r ,c ( r )). This means, that request r requires the transport of a con-
tainer of size c ( r ) from the pickup location r + to the delivery location r .The
container size c ( r )) is measured in twenty-foot equivalent units (TEU) and only
c ( r ) = 1 (a 20-foot container) or c ( r ) = 2 (a 40-foot container) are allowed values.
Import and export requests are regular PDP requests, i.e., both the pickup
location as well as the delivery location are given. In an import request, a
loaded container of known size has to be delivered from a terminal to a cus-
tomer location, i.e., ( r + ,r ,c ( r ))
∈N TERMINAL ×N CUSTOMER ×{
.An
export request, on the other hand, requires the transportation of a loaded con-
tainer of known size from a customer location to a terminal, i.e., ( r + ,r ,c ( r ))
1; 2
}
N CUSTOMER ×N TERMINAL ×{
. We distinguish these two request types
for two reasons. On the one hand, this fact may be used in providing tighter
model formulations in the future or it may be exploited by a heuristic. This
distinction is also used in some related approaches and therefore provides some
consistency with the literature, e.g. [14], [6], [12].
By means of a provide request , a given customer requires an empty container.
That is, the delivery location r of a provide request r is given. However, the used
pickup location is part of the decision problem. We assume, it is always possible
to pickup an empty container from a container depot. However, it is also possible
to pickup a container from a customer with a surplus of empty containers. Node
H in Fig. 1 represents the delivery location of a provide request, i.e., H requires
1; 2
}
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