Enriching the tactical network design of express service carriers with fleet scheduling characteristics

Express service carriers provide time-guaranteed deliveries of parcels via a network consisting of nodes and hubs. In this, nodes take care of the collection and delivery of parcels, and hubs have the function to consolidate parcels in between the nodes. The tactical network design problem assigns nodes to hubs, determines arcs between hubs, and routes parcels through the network. Afterwards, fleet scheduling creates a schedule for vehicles operated in the network. The strong relation between flow routing and fleet scheduling makes it difficult to optimise the network cost. Due to this complexity, fleet scheduling and network design are usually decoupled. We propose a new tactical network design model that is able to include fleet scheduling characteristics (like vehicle capacities, vehicle balancing, and drivers' legislations) in the network design. The model is tested on benchmark data based on instances from an express provider, resulting in significant cost reductions

Enriching the Tactical Network Design of Express Service Carriers with Fleet Scheduling Characteristics

Express service carriers provide time-guaranteed deliveries of parcels via a network consisting of nodes and hubs. In this, nodes take care of the collection and delivery of parcels, and hubs have the function to consolidate parcels in between the nodes. The tactical network design problem assigns nodes to hubs, determines arcs between hubs, and routes parcels through the network. Afterwards, fleet scheduling creates a schedule for vehicles operated in the network. The strong relation between flow routing and fleet scheduling makes it difficult to optimise the network cost. Due to this complexity, fleet scheduling and network design are usually decoupled. We propose a new tactical network design model that is able to include fleet scheduling characteristics (like vehicle capacities, vehicle balancing, and drivers’ legislations) in the network design. The model is tested on benchmark data based on instances from an express provider, resulting in significant cost reductions.express service carriers;freight transportation;tactical hub network design;integer programming;fleet scheduling;heuristics

The design of road and air networks for express service providers

Express service providers move packages (i.e. parcels, documents, or pieces of freight) from senders to receivers under various but guaranteed service level agreements. These service level agreements specify date and time of collection at the sender, and receiving at the customer. Research in this dissertation is dedicated to the design of so-called express line-haul transports from the first consolidation point, the origin depot, to the last consolidation point, the destination depot. The line-haul transport is commonly organized either via road or via air. Hub locations are used to sort packages of incoming line-hauls, and to consolidate and load these packages on the outgoing line-hauls. The strategic network design problem is concerned with decisions on these hub locations in the network: how many hubs are needed and where should these be located, and which line-hauls are unloaded and loaded at each hub location? The tactical planning level at express service providers contains decisions on package routings from origin to destination and asset usages. This dissertation focusses on the design of the strategic and tactical line-haul network for road transport in Part I of this dissertation and deals with similar topics for air transport in Part II of this dissertation. In the concluding chapters we present a general review of strategic and tactical network design for express service providers and point to directions for future research

Enriching the tactical network design of express service carriers with fleet scheduling characteristics

Express service carriers provide time-guaranteed deliveries of parcels via a network consisting of nodes and hubs. In this, nodes take care of the collection and delivery of parcels, and hubs have the function to consolidate parcels in between the nodes. The tactical network design problem assigns nodes to hubs, determines arcs between hubs, and routes parcels through the network. Afterwards, fleet scheduling creates a schedule for vehicles operated in the network. The strong relation between flow routing and fleet scheduling makes it difficult to optimise the network cost. Due to this complexity, fleet scheduling and network design are usually decoupled. We propose a new tactical network design model that is able to include fleet scheduling characteristics (like vehicle capacities, vehicle balancing, and drivers’ legislations) in the network design. The model is tested on benchmark data based on instances from an express provider, resulting in significant cost reductions

Scheduling movements in the network of an express service provider

Express service providers manage shipments from senders to receivers under strict service level agreements. Such shipments are usually not sufficient to justify a single transportation, so it is preferred to maximize consolidation of these shipments to reduce cost. The consolidation is organized via depots and hubs: depots are local sorting centers that take care of the collection and delivery of the parcels at the customers, and hubs are used to consolidate the transportation between the depots. A single transportation between two locations, carried out by a certain vehicle at a specific time, is defined as a movement. In this paper, we address the problem of scheduling all movements in an express network at minimum cost. Our approach allows to impose restrictions on the number of arriving/departing movements at the hubs so that sufficient handling capacity is ensured. As the movement scheduling problem is complex, it is divided into two parts: one part concerns the movements between depots and hubs; the other part considers the movements between the hubs. We use a column generation approach and a local search algorithm to solve these two subproblems, respectively. Computational experiments show that by using this approach the total transportation costs are decreased

Supply chain-wide optimization at TNT Express

The application of operations research (OR) at TNT Express during the past seven years has significantly improved decision-making quality and resulted in cost savings of 207 million euros. The global optimization (GO) program initiative has led to the development of a suite of optimization solutions to assist the operating units of TNT Express to improve their package delivery in road and air networks. To create and deploy these solutions, we established communities of practice (CoPs), at which internal and external subject matter experts meet three times annually at an internal conference. We also created a unique two-year learning environment, the GO academy, where employees of TNT Express are taught the principles, use, and deployment of optimization techniques. As a result of these combined initiatives, OR is now an effective part of the core values at TNT Express

Language dominance in Turkish-German bilinguals: Methodological aspects of measurements in structurally different languages

The purpose of this study is to establish measures of language dominance in bilinguals who speak structurally different languages, in our case German and Turkish, with tools that are based on fluency and oral proficiency. A 'balanced' bilingual with equal proficiency in two (or more) languages is hardly ever found (e.g. Grosjean, 1982; Olsson, & Sullivan, 2005) but the identification of the dominant language is a huge methodological problem, especially in studies of structurally different languages (see Daller, van Hout, & Treffers-Daller, 2003). The participants in the present study are a group of Turkish-German bilinguals who grew up in Germany and returned to Turkey during their school career, the so-called 'returnees' (n = 60), and a group of Turkish secondary school students who grew up in Turkey and learned German as an L2, the so-called control group (n = 55). We firstly establish the language dominance of the two groups with a C-test. We then use oral picture descriptions in both languages to measure a variety of fluency measures, both manually and using scripts written in 'Praat' (Boersma & Weenink, 2007). On the basis of these scores, we are able to develop measures of fluency that correlate highly with the C-test scores and have a highly predictive value in a logistic regression in the prediction of group membership (returnee or member of the control group). We conclude that this corroborates the validity of the measures. Overall we conclude that it is possible to develop measures of language dominance based on fluency and overall oral proficiency.© The Author(s) 2010