The delivery dispatching problem with time windows for urban consolidation centers

This paper addresses the dispatching problem faced by an urban consolidation center. The center receives orders according to a stochastic arrival process and dispatches them in batches for the last-mile distribution. The operator of the center aims to find the cost-minimizing consolidation policy, depending on the orders at hand, preannounced orders, and stochastic arrivals. We present this problem as a variant of the delivery dispatching problem that includes dispatch windows and define a corresponding Markov decision model. Larger instances of the problem suffer from intractably large state-, outcome-, and action spaces. We propose an approximate dynamic programming (ADP) algorithm that can handle such instances, using a linear value function approximation to estimate the downstream costs. To design the value function approximation, we construct various sets of basis functions, numerically evaluate their suitability, and discuss the properties of good basis functions for the dispatching problem. Numerical experiments on toy-sized instances show that the best set of basis functions approximates the optimal values with an error of less than 3%. To cope with large action spaces, we formulate an integer linear program to be used within our ADP algorithm. We evaluate the performance of ADP policies against four benchmark policies: two heuristic policies, a direct cost minimization policy, and a post-decision rollout policy. We test the performance of ADP on a variety of networks. ADP consistently outperforms the benchmark policies, performing particularly well when there is sufficient flexibility in dispatch times

The delivery dispatching problem with time windows for urban consolidation centers

This paper addresses the dispatch decision problem faced by an urban consolidation center. The center receives orders according to a stochastic arrival process, and dispatches them for the last-mile distribution in batches. The operator of the center aims to fi nd the cost-minimizing consolidation policy, depending on the orders at hand, pre-announced orders, and stochastic arrivals. We present this problem as a variant of the Delivery Dispatching Problem that includes dispatch windows, and model it as a Markov decision problem. For toy-sized instances, we solve this model to optimality. Through numerical experiments on these instances, we show that we approximate the optimal values with an error of less than 2%. Larger instances suff er from intractably large state-, outcome-, and action spaces. We propose an Approximate Dynamic Programming (ADP) algorithm that can handle such instances, using value function approximation to estimate the downstream costs. To cope with large action spaces - with sizes up to 2120 in our experiments - we formulate an integer linear program to be used within our ADP algorithm. To evaluate the performance of our ADP policies, we test against various benchmark policies, including a lookahead policy based on scenario sampling. We test the performance of ADP on a variety of networks. When the dispatching problem provides su fficient fl+6exibility in dispatch times, ADP outperforms our myopic benchmark policies by more than 15%, and lookahead policies by over 10%

An Approximate Dynamic Programming Approach to Urban Freight Distribution with Batch Arrivals

We study an extension of the delivery dispatching problem (DDP) with time windows, applied on LTL orders arriving at an urban consolidation center. Order properties (e.g., destination, size, dispatch window) may be highly varying, and directly distributing an incoming order batch may yield high costs. Instead, the hub operator may wait to consolidate with future arrivals. A consolidation policy is required to decide which orders to ship and which orders to hold. We model the dispatching problem as a Markov decision problem. Dynamic Programming (DP) is applied to solve toy-sized instances to optimality. For larger instances, we propose an Approximate Dynamic Programming (ADP) approach. Through numerical experiments, we show that ADP closely approximates the optimal values for small instances, and outperforms two myopic benchmark policies for larger instances. We contribute to literature by (i) formulating a DDP with dispatch windows and (ii) proposing an approach to solve this DDP

Efficient heuristic algorithms for location of charging stations in electric vehicle routing problems

Indexación: Scopus.This work has been partially supported by CONICYT FONDECYT by grant 11150370, FONDEF IT17M10012 and the “Grupo de Logística y Transporte” at the Universidad del Bío-Bío.. This support is gratefully acknowledged.Eco-responsible transportation contributes at making a difference for companies devoted to product delivery operations. Two specific problems related to operations are the location of charging stations and the routing of electric vehicles. The first one involves locating new facilities on potential sites to minimise an objective function related to fixed and operational opening costs. The other one, electric vehicle routing problem, involves the consolidation of an electric-type fleet in order to meet a particular demand and some guidelines to optimise costs. It is determined by the distance travelled, considering the limited autonomy of the fleet, and can be restored by recharging its battery. The literature provides several solutions for locating and routing problems and contemplates restrictions that are closer to reality. However, there is an evident lack of techniques that addresses both issues simultaneously. The present article offers four solution strategies for the location of charging stations and a heuristic solution for fleet routing. The best results were obtained by applying the location strategy at the site of the client (relaxation of the VRP) to address the routing problem, but it must be considered that there are no displacements towards the recharges. Of all the other three proposals, K-means showed the best performance when locating the charging stations at the centroid of the cluster. © 2012-2018. National Institute for R and D in Informatics.https://sic.ici.ro/wp-content/uploads/2018/03/Art.-8-Issue-1-2018-SIC.pd

Gain-Sharing in Urban Consolidation Centers

Urban consolidation centers provide the logistical infrastructure for cooperation among less-than-truckload carriers with contiguous destinations. The rising number of initiatives to establish and operate urban consolidation centers and their low success rates signal the need for better mechanisms to manage cooperation in this context. We introduce and study cooperative situations comprising a set of carriers with time sensitive deliveries who can consolidate their cargo to obtain savings. We introduce the class of Dispatch Consolidation (DC) games and search for ways to fairly allocate the obtained savings among the participating carriers. When delivery capacities are not restrictive, i.e. when waiting costs trigger truck dispatches, we show that stable allocations in the core always exist and can, in their entirety, be found by solving a compact linear program. With restrictive capacities, however, the core of a DC game may become empty. We introduce the notion of component-wise core for DC games to preserve stability first and foremost among the carriers whose deliveries are dispatched together in the chosen optimal solutions. The novelty of our approach is to link the stability requirements of an allocation rule with the structure of selected solutions for the underlying optimization problems. We characterize the component-wise cores of DC games, prove their non-emptiness, and suggest proportionally calculated allocations therein. Finally, we discuss a refinement of component-wise core allocations that minimizes envy among the carriers who are dispatched separately

Last-mile logistics optimization in the on-demand economy

L'abstract è presente nell'allegato / the abstract is in the attachmen

The two-echelon capacitated vehicle routing problem: models and math-based heuristics

Multiechelon distribution systems are quite common in supply-chain and logistics. They are used by public administrations in their transportation and traffic planning strategies, as well as by companies, to model own distribution systems. In the literature, most of the studies address issues relating to the movement of flows throughout the system from their origins to their final destinations. Another recent trend is to focus on the management of the vehicle fleets required to provide transportation among different echelons. The aim of this paper is twofold. First, it introduces the family of two-echelon vehicle routing problems (VRPs), a term that broadly covers such settings, where the delivery from one or more depots to customers is managed by routing and consolidating freight through intermediate depots. Second, it considers in detail the basic version of two-echelon VRPs, the two-echelon capacitated VRP, which is an extension of the classical VRP in which the delivery is compulsorily delivered through intermediate depots, named satellites. A mathematical model for two-echelon capacitated VRP, some valid inequalities, and two math-heuristics based on the model are presented. Computational results of up to 50 customers and four satellites show the effectiveness of the methods developed