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Vehicle Routing
Problems
Massimo Paolucci
(paolucci@dist.unige.it)
010-353 2996
DIST – Università di Genova
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VRP – Massimo Paolucci
Vehicle Routing Problems
Vehicle Routing Problems (VRP) deal with the
management of pickup and/or delivery activities
Critical problems, in particular in short distance
transportation
Operational decisions: how the available fleet of vehicles
(resources) can be efficiently used to satisfy a given
service demand according to a set of operational
requirements?
Vehicle Routing: define the routes and possibly the
schedule for the available vehicles

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VRP – Massimo Paolucci
Vehicle Routing Problems
VRPs include:
Static problems: the service demand is fixed and a priori known
Dynamic problems: all or part of the service demand may become
known when the vehicles have already started their service (the
vehicle routes may be defined or changed on-line)
Main assumptions for the problems considered in the
following:
The problems are static
The available vehicles are homogeneous (every vehicle provide
the same kind of service)
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VRP – Massimo Paolucci
VRP – Characteristics and Components
Freight transportation provided by vehicles through a route
network
Main components:
Road network
Customers
Vehicles
Depots
Drivers
Operational constraints:
global
for single routes
Optimization objectives

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VRP – Massimo Paolucci
VRP – Characteristics and Components
The road network:
A graph G=(V, A), G=(V, E) or G=(V, A∪ E)
Directed, undirected or mixed
Sparse vs Dense
Sparse ⇒ |A|=O(|V|)
Dense ⇒ |A|=O(|V|
2
)
Undirected graph:
large scale road network (countries, regions)
Directed graph:
small scale road network (cities)
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VRP – Massimo Paolucci
The road network:
Vertices
depots, customers, road intersections
V={0, 1, …, n}
Arcs
roads
directed (i, j)∈A or undirected e∈E
length, or travel cost c
ij
∀
(i, j)∈A
travel time t
ij
∀
(i, j)∈A
VRP – Characteristics and Components
c
ij
j
0
i

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VRP – Massimo Paolucci
VRP – Characteristics and Components
The road network:
The triangle inequality
j
i
k
c
ij
c
ik
c
kj
c
ij
≤ c
ik
+ c
kj
∀i, j, k
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VRP – Massimo Paolucci
VRP – Characteristics and Components
Customers:
The entities requiring service
Associated with vertices or arcs
Service demand ⇒ quantity of goods or materials to be
delivered or picked up
Characteristics:
Service time windows
Desired service start time (with penalties)
Service time (load/unload)
Vehicle compatibility
Possibility of splitting service

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VRP – Massimo Paolucci
VRP – Characteristics and Components
Vehicles:
Fleet size (fixed or variable)
Company or outsourced fleet (fixed vehicle cost)
Depot of reference (single, multiple, possibility of change)
Vehicle capacity (maximum load allowed; weight, volume)
Freight compatibility (perishable goods, dangerous materials)
Compatibility with streets
Load/unload procedure
Costs (associated with mileage, time, fuel, journey, load)
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VRP – Massimo Paolucci
VRP – Characteristics and Components
Drivers
Employee workers or vehicle owners
Union and contract conditions
Working periods, shifts and breaks
Availability and possibility of overtime
Depots
Single or multiple
Number and type of available vehicles
Set of a priori assigned customers
⇒ decomposable problems
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