Search results for "operation"
showing 10 items of 2969 documents
Viability of new road infrastructure with heterogeneous users
2011
This paper explores the importance of heterogeneity in value of time and route choice when assessing the viability of new road infrastructure to alleviate congestion problems. The model incorporates strategic interaction between road operators in a cost-benefit framework and several competitive regimes are considered. It is then employed to establish the financial and socio-economic viability of a congestion pricing demonstration entering Madrid city centre, where road users have to choose between a free but highly congested road and a priced free-flowing road (semi-private regime). A logit estimation is undertaken with information from a questionnaire among road users in the Eastern Madrid…
Optimal Transit Network Design
2019
In this chapter, the optimal transit network design is under investigation. A special kind of transport is assumed to be given the best traffic conditions in a road network (the smallest amount of travel time between origins and destinations). Optimality criteria for transit network design in case of selfish routing are defined in the first section. The Sect. 7.2 is devoted to the estimation of selfish traffic assignment in a network with a transit subnetwork. Optimality criteria for transit network design in case of competitive drivers’ groups routing are defined in the Sect. 7.3. The Sect. 7.4 is devoted to traffic assignment in case of competitive drivers’ groups routing in a network wit…
Efficient GRASP+VND and GRASP+VNS metaheuristics for the traveling repairman problem
2011
Abstract: The traveling repairman problem is a customer-centric routing problem, in which the total waiting time of the customers is minimized, rather than the total travel time of a vehicle. To date, research on this problem has focused on exact algorithms and approximation methods. This paper presents the first metaheuristic approach for the traveling repairman problem.
Improved heuristics for the regenerator location problem
2014
Telecommunication systems use optical signals to transmit information. The strength of a signal in an optical network deteriorates and loses power as it goes farther from the source, mainly due to attenuation. Therefore, to enable the signal to arrive its intended destination with good quality, it is necessary to regenerate the signal periodically using regenerators. These components are relatively expensive and therefore it is desirable to deploy as few of them as possible in the network. In the regenerator location problem (RLP), we are given an undirected graph, positive edge lengths, and a parameter specifying the maximum length that a signal can travel before its quality deteriorates a…
Crisis and Opportunities Variables always Addressed Simultaneously in Effective Management
2013
Abstract Understanding the causes, duration and consequences of the crisis and the means to exit it are far from being regarded as sufficiently understood and operationalized. From the general components of the crisis, there was a necessity to be defined and managed separately the subjective component (disorientation, confusion) and the objective component, which are unequivocally different. They have to be operationalized into strategies, programs and tactical procedures to traverse and overcome the crisis with minimal loss. The paper also deals with the opportunities that crisis can create and with the measures necessary to identify and exploit these.
Solving a large multicontainer loading problem in the car manufacturing industry
2017
Abstract Renault, a large car manufacturer with factories all over the world, has a production system in which not every factory produces all the parts required to assemble a vehicle. Every day, large quantities of car parts are sent from one factory to another, defining very large truck/container transportation problems. The main challenge faced by the Renault logistics platforms is to load the items into trucks and containers as efficiently as possible so as to minimize the number of vehicles sent. Therefore, the problem to be solved is a multicontainer loading problem in which, besides the usual geometric constraints preventing items from overlapping and exceeding the dimensions of the c…
Bidirectional labeling for solving vehicle routing and truck driver scheduling problems
2020
Abstract This paper studies the vehicle routing and truck driver scheduling problem where routes and schedules must comply with hours of service regulations for truck drivers. It presents a backward labeling method for generating feasible schedules and shows how the labels generated with the backward method can be combined with labels generated by a forward labeling method. The bidirectional labeling is embedded into a branch-and-price-and-cut approach and evaluated for hours of service regulations in the United States and the European Union. Computational experiments show that the resulting bidirectional branch-and-price-and-cut approach is significantly faster than unidirectional counterp…
Algorithms for Pallet Building and Truck Loading in an Interdepot Transportation Problem
2016
This paper deals with the problem of a logistics company that has to serve its customers by first putting the products on pallets and then loading the pallets into trucks. Besides the standard geometric constraints of products not overlapping each other and not exceeding the dimensions of pallets and trucks, in this real problem, there are many other constraints, related to the total weight of the load, the maximum weight supported by each axle, and the distribution of the load inside the truck. Although the problem can be decomposed into two phases, pallet loading and truck loading, we have taken a combined approach, building and placing pallets at the same time. For each position in the t…
A Branch-and-Cut Algorithm for the Single Truck and Trailer Routing Problem with Satellite Depots
2016
International audience; In the single truck and trailer routing problem with satellite depots (STTRPSD), a truck with a detachable trailer based at a main depot must serve the demand of a set of customers accessible only by truck. Therefore, before serving the customers, it is necessary to detach the trailer in an appropriate parking place (called either a satellite depot or a trailer point) and transfer goods between the truck and the trailer. This problem has applications in milk collection for farms that cannot be reached using large vehicles. In this work we present an integer programming formulation of the STTRPSD. This formulation is tightened with several families of valid inequaliti…
Branch-and-Price-and-Cut for the Truck-and-Trailer Routing Problem with Time Windows
2018
In this paper, we present a new branch-and-price-and-cut algorithm to solve the truck-and-trailer routing problem with time windows (TTRPTW) and two real-world extensions. In all TTRPTW variants, the fleet consists of one or more trucks that may attach a trailer. Some customers are not accessible with a truck-and-trailer combination, but can however be serviced by one if the trailer is previously detached and parked at a suitable location. In the first extension, the planning horizon comprises two days and customers may be visited either on both days or only once, in which case twice the daily supply must be collected. The second extension incorporates load transfer times depending on the …