This paper is a survey of
location-routing: a relatively new branch of locational analysis that takes into account vehicle routing aspects. We propose a classification scheme and look at a number of ...problem variants. Both exact and heuristic algorithms are investigated. Finally, some suggestions for future research are presented.
The Vehicle Routing Problem with Pickups and Deliveries (VRPPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods. We do not make the ...assumption common in the VRPPD literature, that goods may only be picked up after all deliveries have been completed. We also eschew the concept of insertion and propose a method that treats pickups and deliveries in an integrated manner. This method finds a solution to the corresponding VRP problem and modifies this solution to make it feasible for the VRPPD. Such modification is achieved mainly by heuristic routines taken from VRP methodology but modified such that their aim becomes the reduction of infeasibilities, although a number of problem-specific routines are also constructed. To render our procedures efficient when checking feasibility, we built appropriate mathematical relationships to describe changes in the maximum load of routes. Furthermore, several enhancements are introduced. Our methodology is also capable of solving multi-depot problems, which has not been done before for this challenging general version of the VRPPD. The methods are tested for single and multiple depot problems with encouraging results.
This study is inspired by a challenging logistic problem encountered in the cleaning service sector. The company wishes to solve the consistent vehicle routeing problem over a three-month planning ...horizon. The company has a heterogeneous vehicle fleet to guarantee multiple frequencies of visits to its customers. The objective is to minimise the number of vehicles used and the total distance travelled. This problem is a generalisation of the periodic vehicle routeing problem. We decompose the problem into two sub-problems, namely, the planning and routeing optimisation sub-problems. We construct a mathematical model for the former and a large neighbourhood search for the latter. We evaluate the performance of our approach using the results of the industrial partner and instances from the literature on problems that are closely related to our case study. Our approach is found to be effective and robust. Our results outperform the existing company's plan in terms of solution quality, and staff convenience, and speed. We also discovered new best solutions on some of the instances from the literature.
In this paper a new VRP variant the Multiple Trip Vehicle Routing Problem with Backhauls (MT-VRPB) is investigated. The classical MT-VRP model is extended by including the backhauling aspect. An ILP ...formulation of the MT-VRPB is first presented and CPLEX results for small and medium size instances are reported. For large instances of the MT-VRPB a Two-Level VNS algorithm is developed. To gain a continuous balanced intensification and diversification during the search process VNS is embedded with the sequential VND and a multi-layer local search approach. The algorithm is tested on a set of new MT-VRPB data instances which we generated. Interesting computational results are presented. The Two-Level VNS produced excellent results when tested on the special variant of the VRPB.
•An introduction of a new VRP variant – MT-VRPB – an ILP formation of the problem.•CPLEX implementation to test the model and producing optimal solutions and bounds.•A sweep-first-assignment-second that produces initial feasible solution quickly.•A Two-Level VNS algorithm to solve the MT-VRPB efficiently.•A new MT-VRPB data set is generated that could be used for benchmarking.•The developed algorithm is useable for the classical VRPB.
•A dynamic emergency route planning model for major chemical accidents was proposed.•The Dijkstra algorithm is modified to solve the multi-objective optimization problem for the emergency route ...selection.•An individual emergency risk classification method for major chemical accidents was obtained.
Combining scenario construction with the characteristics of individual emergency behavior is necessary for the emergency route planning of major chemical accidents. We investigated this challenging decision problem and constructed a multi-indicator emergency risk assessment method that considers the evacuation speed of different population types and health consequences caused by various risk components. We also designed a modified Dijkstra algorithm to solve this dynamic multi-objective route planning problem. The comparative experiment results demonstrated that the proposed algorithm performs relatively better than the traditional Dijkstra algorithm. Finally, we performed extensive case studies where our simulation results demonstrate that the proposed model provides reliable and practical emergency route planning services for various personnel types under different accident scenarios. Compared with the commonly used single-dimensional assessment method, this comprehensive and informative assessment of the emergency risks faced by the population in different regions could serve as a useful reference for the formulation and implementation of emergency plans in case of major chemical accidents.
•Investigation of a multi-period problem in election logistics and campaign planning.•Time-dependent rewards, co-existence of open and closed tours, repeated visits.•Development of a novel ...mixed-integer linear programming formulation.•Design of a two-phase matheuristic for efficient and effective solutions.•Testing on real-life instances derived from election campaigns in Turkey.
In this paper we investigate a novel logistical problem. The goal is to determine daily tours for a traveling salesperson who collects rewards from activities in cities during a fixed campaign period. We refer to this problem as the Roaming Salesman Problem (RSP) motivated by real-world applications including election logistics, touristic trip planning and marketing campaigns. RSP can be characterized as a combination of the traditional Periodic TSP and the Prize-Collecting TSP with static arc costs and time-dependent node rewards. Commercial solvers are capable of solving small-size instances of the RSP to near optimality in a reasonable time. To tackle large-size instances we propose a two-phase matheuristic where the first phase deals with city selection while the second phase focuses on route generation. The latter capitalizes on an integer program to construct an optimal route among selected cities on a given day. The proposed matheuristic decomposes the RSP into as many subproblems as the number of campaign days. Computational results show that our approach provides near-optimal solutions in significantly shorter times compared to commercial solvers.
This paper studies the multi-period travelling politician problem whose objective is to maximise the net benefit accrued by a party leader during a fixed campaign period. The problem is also ...characterised by flexible depots since the daily tours realised by the party leader may not start and end at the same city. A hybrid multi-start Iterated Local Search method complemented with a Variable Neighbourhood Descent is developed to solve the problem heuristically. Two constructive procedures are devised to generate initial feasible solutions. The proposed method is tested on 45 problem instances involving 81 cities and 12 towns in Turkey. Computational results show that the hybrid metaheuristic approach outperforms a recently proposed two-phase matheuristic by producing 7 optimal solutions and 17 new best solutions. In addition, interesting practical insights are provided using scenario analysis that could assist campaign planners in their strategic decisions.
An iterative scheme which is based on a dynamic fixation of the variables is developed to solve the 0-1 multidimensional knapsack problem. Such a scheme has the advantage of generating memory ...information, which is used on the one hand to choose the variables to fix either permanently or temporarily and on the other hand to construct feasible solutions of the problem. Adaptations of this mechanism are proposed to explore different parts of the search space and to enhance the behaviour of the algorithm. Encouraging results are presented when tested on the correlated instances of the 0-1 multidimensional knapsack problem.
In physical distribution the location of depots and vehicle routes are interdependent problems, but they are usually treated independently. Location-routing is the study of solving locational ...problems such that routing considerations are taken into account. We present an iterative heuristic for the location-routing problem on the plane. For each depot the Weber problem is solved using the end-points of the routes found previously as input nodes to the Weiszfeld procedure. Although the improvements found are usually small they show that it pays not to ignore the routing aspects when solving continuous location problems. Possible research avenues in continuous location-routing will also be suggested.
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