Environmental Engineering Reference
In-Depth Information
nature of transport (Taniguchi et al.
2001
; Taniguchi and Thompson
1999
,
2001
),
on access restrictions (Munuzuri and Van Duin
2013
) and on pickup and delivery
strategies, among others. Since one-tier systems are well studied in the literature,
we aim to extend Crainic's (
2008
) work for two-tier systems. Note that this chapter
is directed to both researchers and practitioners of different disciplines so instead
of an in-depth overview of operations research algorithms it presents the main
categories of problems and methods. Detailed literature reviews on the subject are
found in Drexl (
2012
), Gonzalez-Feliu (
2013b
) and Mancini (
2013b
).
In two-tier systems, two fleets of heterogeneous vehicles synchronize to deliver
time-dependent freight demands within customer time windows, with little or no
waiting room at (most) transfer stations. To deal with such systems, several new
problems and challenges can be observed, but they can be grouped into two main
categories. The first derives from the multi-stage nature of the transportation
system, and all questions related to connexion among stages (Gonzalez-Feliu
2012a
) and synchronization (Drexl
2012
) and seeks to study the problem as a two-
stage system following the concept of multi-stage transport systems (Kreutzberger
2008
; Gonzalez-Feliu
2013a
). The second is related to the multi-trip nature of
second-stage transport schemes (Nguyen et al.
2012
) and consists on taking into
account different e tactical planning (Crainic
2008
). Indeed, in such systems it is
considered that the first tier vehicles are planned in a first time, giving an overall
idea of the second tier, and this last is refined in a second time (Crainic et al.
2009
).
Other issues are the different types of transport modes, vehicles and routes that can
be involved in such schemes (Crainic et al.
2012
), collaboration among partners
(Gonzalez-Feliu et al.
2013b
) or the integration of new services like time-con-
strained deliveries or pickup and delivery services (Crainic et al.
2012
) but they
can be included in the two main categories of approaches.
We present below both categories of approaches, presenting the main concepts
and assumptions related to them and the most popular solving methods shown in
the literature.
3.1 Problem Definition and Variants
We observe in the literature several declinations of the problem, arising on two
main questions of vocabulary. The first is related to the hierarchic nature of the
problem (Min et al.
1998
): several terms, like level, echelon, tier or stage are used.
To make practitioners more familiar with the problems, and avoid confusion with
multi-echelon logistics systems, we will use the definition of Min et al. (
1998
) and
Gonzalez-Feliu (
2013a
), calling them multi-stage transport systems. The second is
the name of the combinatorial optimization problem that can be defined to opti-
mise such systems. Three main problems have been defined in literature (multi-
stage vehicle routing, multi-stage location routing and truck-and-trailer vehicle
routing). However, all three problems are declinations of the same model, as stated
in Nagy and Salhi (
2007
). For that reason, we will call such problems multi-stage
Search WWH ::
Custom Search