Environmental Engineering Reference
In-Depth Information
• restocking trip models,
- quantity model sub-system; it allows us to estimate the quantity origin-
destination (O-D) matrices characterized by freight types; this step highlights
the effects due to implementation of strategic actions (e.g. urban land-use
governance) on the locations of logistic facilities (e.g. warehouses and dis-
tribution centers) and retail activities (e.g. local shops or shopping centers);
- delivery model sub-system; it allows us to convert quantities into delivery
O-D flows; the delivery flows are also split in terms of transport services used
(e.g. retailer on own account, wholesaler on own account and carrier); this
step serves specifically to study the definition of restocking journeys in terms
of transport service and shipment size (i.e. tactical level);
- vehicle model sub-system; it allows us to obtain the vehicle O-D flows sat-
isfying the given delivery O-D matrices, and investigate the tours undertaken
to restock the study area; in particular, the tours are characterized by departure
time, number of stops, vehicle used, and sequence of delivery locations.
4.2 Shopping Trip Models
Following Nuzzolo and Comi ( 2013b ) and assuming that the decision-maker (i.e.
end consumer) is in zone o, the choice dimensions involved are: the number of
trips (x) for shopping, the destination (d) and type of shop (k; e.g. small, medium
and large), the transport mode (or sequence of modes; m). The global demand
function can be decomposed into the product of sub-models, each of which relates
to one or more choice dimensions. The sequence most often used is the following:
D i od
¼ D i o :
½ p i
p i
p i
½
skm
½
k = so
½
d = kso
½
m = dkso
ð 1 Þ
where
• D o i [skm] is the average number of trips with origin in zone o undertaken by end
consumers of category i for purchasing freight of type s in retail outlet k located
in zone d by using transport mode m;
• D o. i [s] is the mean number of ''relevant'' trips undertaken by end-consumers
belonging to category i for shopping freight of type s with origin in zone
o obtained by a trip generation model;
• p i [k/so] is the probability that users, undertaking a trip from o, travel for pur-
chasing at shop type k, obtained by a shop type choice model;
• p i [d/kso] is the probability that users, undertaking a trip from o, travel to des-
tination zone d for purchasing at shop type k, obtained by a location shop model;
• p i [m/dkso] is the probability that users, traveling between o and d for purchasing
in shop type k, use transport mode m obtained by a modal choice or split model.
Finally, the quantities required by each zone to satisfy end-consumer needs can
be obtained by introducing the quantity purchase model (Russo and Comi 2012 ).
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