14,152 research outputs found
On green routing and scheduling problem
The vehicle routing and scheduling problem has been studied with much
interest within the last four decades. In this paper, some of the existing
literature dealing with routing and scheduling problems with environmental
issues is reviewed, and a description is provided of the problems that have
been investigated and how they are treated using combinatorial optimization
tools
Vehicle routing under time-dependent travel times: the impact of congestion avoidance
Daily traffic congestions form major problems for businesses such\ud
as logistical service providers and distribution firms. They cause\ud
late arrivals at customers and additional hiring costs for the truck\ud
drivers. The additional costs of traffic congestions can be reduced\ud
by taking into account and avoid well-predictable traffic congestions\ud
within off-line vehicle route plans. In the literature, various strategies\ud
are proposed to avoid traffic congestions, such as selecting alternative routes, changing the customer visit sequences, and changing the\ud
vehicle-customer assignments. We investigate the impact of these and\ud
other congestion avoidance strategies in off-line vehicle route plans on\ud
the performance of these plans in reality. For this purpose, we develop\ud
a set of VRP instances on real road networks, and a speed model that\ud
inhabits the main characteristics of peak hour congestion. The instances are solved for different levels of congestion avoidance using a\ud
modified Dijkstra algorithm and a restricted dynamic programming\ud
heuristic. Computational experiments show that 99% of late arrivals\ud
at customers can be eliminated if traffic congestions are accounted for\ud
off-line. On top of that, almost 70% of the extra duty times caused by\ud
the traffic congestions can be eliminated by clever avoidance strategies
A matheuristic approach for the Pollution-Routing Problem
This paper deals with the Pollution-Routing Problem (PRP), a Vehicle Routing
Problem (VRP) with environmental considerations, recently introduced in the
literature by [Bektas and Laporte (2011), Transport. Res. B-Meth. 45 (8),
1232-1250]. The objective is to minimize operational and environmental costs
while respecting capacity constraints and service time windows. Costs are based
on driver wages and fuel consumption, which depends on many factors, such as
travel distance and vehicle load. The vehicle speeds are considered as decision
variables. They complement routing decisions, impacting the total cost, the
travel time between locations, and thus the set of feasible routes. We propose
a method which combines a local search-based metaheuristic with an integer
programming approach over a set covering formulation and a recursive
speed-optimization algorithm. This hybridization enables to integrate more
tightly route and speed decisions. Moreover, two other "green" VRP variants,
the Fuel Consumption VRP (FCVRP) and the Energy Minimizing VRP (EMVRP), are
addressed. The proposed method compares very favorably with previous algorithms
from the literature and many new improved solutions are reported.Comment: Working Paper -- UFPB, 26 page
Planning and Scheduling Transportation Vehicle Fleet in a Congested Traffic Environment
Transportation is a main component of supply chain competitiveness since it plays a major role in the inbound, inter-facility, and outbound logistics. In this context, assigning and scheduling vehicle routing is a crucial management problem. Despite numerous publications dealing with efficient scheduling methods for vehicle routing, very few addressed the inherent stochastic nature of travel times in this problem. In this paper, a vehicle routing problem with time windows and stochastic travel times due to potential traffic congestion is considered. The approach developed introduces mainly the traffic congestion component based on queueing theory. This is an innovative modeling scheme to capture the stochastic behavior of travel times. A case study is used both to illustrate the appropriateness of the approach as well as to show that time-independent solutions are often unrealistic within a congested traffic environment which is often the case on the european road networkstransportation; vehicle fleet; planning; scheduling; congested traffic
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