Forest Road Network and Transportation Engineering – State and Perspectives

The paper reviews traditional and computer-assisted road network layout approaches and brings them together in an overall stream of development. It results in the main finding that changes in the representation of the road network layout problem triggered major scientific advancements. A systematic, 2D transport geometry representation emerged in the 1870s and led to the mathematical derivation of optimal road spacing. The representation of road network and harvest layout problem as a mathematical graph and the solution of the corresponding linear programming problem, triggered a representational shift in the early 1970s. The broad availability of digital elevation models DEMs at the beginning of the 1990s was another representational innovation, enabling an automatic road route layout on the terrain DEM surface. The most recent shift consisted of systems to semi-automatically, concurrently laying out harvest/transport-network problems on DEMs in the mid-1990s. The review identifies challenges for future research, among which the extension of the concurrent harvest/road-network layout systems for multi-objective functions is the first importance. Considering that scientific advancement is mostly going along with changes in problem representations, research should explore improved representations for lattice type terrain representation, among which triangular irregular network (TIN) meshes seem to be the first interest. Additional paths for improvements are the integration of road network planning with detailed road engineering, the refinement of optimization problems formulations, and the cross-national adaptation of road network planning courses to operations-research-based approaches

Approaches to integrated strategic/tactical forest planning

Traditionally forest planning is divided into a hierarchy of planning phases. Strategic planning is conducted to make decisions about sustainable harvest levels while taking into account legislation and policy issues. Within the frame of the strategic plan, the purpose of tactical planning is to schedule harvest operations to specific areas in the immediate few years and on a finer time scale than in the strategic plan. The operative phase focuses on scheduling harvest crews on a monthly or weekly basis, truck scheduling and choosing bucking instructions. Decisions at each level are to a varying degree supported by computerized tools. A problem that may arise when planning is divided into levels and that is noted in the literature focusing on decision support tools is that solutions at one level may be inconsistent with the results of another level. When moving from the strategic plan to the tactical plan, three sources of inconsistencies are often present; spatial discrepancies, temporal discrepancies and discrepancies due to different levels of constraint. The models used in the papers presented in this thesis approaches two of these discrepancies. To address the spatial discrepancies, the same spatial resolution has been used at both levels, i.e., stands. Temporal discrepancies are addressed by modelling the tactical and strategic issues simultaneously. Integrated approaches can yield large models. One way of circumventing this is to aggregate time and/or space. The first paper addresses the consequences of temporal aggregation in the strategic part of a mixed integer programming integrated strategic/tactical model. For reference, linear programming based strategic models are also used. The results of the first paper provide information on what temporal resolutions could be used and indicate that outputs from strategic and integrated plans are not particularly affected by the number of equal length strategic periods when more than five periods, i.e. about 20 year period length, are used. The approach used in the first paper could produce models that are very large, and the second paper provides a two-stage procedure that can reduce the number of variables and preserve the allocation of stands to the first 10 years provided by a linear programming based strategic plan, while concentrating tactical harvest activities using a penalty concept in a mixed integer programming formulation. Results show that it is possible to use the approach to concentrate harvest activities at the tactical level in a full scale forest management scenario. In the case study, the effects of concentration on strategic outputs were small, and the number of harvest tracts declined towards a minimum level. Furthermore, the discrepancies between the two planning levels were small

Optimization of terrain transportation problems in forestry

A dissertation submitted to Molde University College - Specialized University in Logistics for the degree of Philosophiae Docto

Models and heuristics for forest management with environmental restrictions

Tese de doutoramento, Estatística e Investigação Operacional (Otimização), Universidade de Lisboa, Faculdade de Ciências, 2018The main focus of this thesis was to develop mathematical models and methods in integer programming for solving harvest scheduling problems with environmental restrictions. Constraints on maximum clearcut area, minimum total habitat area, minimum total core area and inter-habitat connectivity were addressed for this purpose. The research was structured in a collection of three papers, each one describing the study of a different forest harvest scheduling problem with respect to the environmental constraints. Problems of papers 1 and 2 aim at maximizing the net present value. A bi objective problem is considered in paper 3. The objectives are the maximization of the net present value and the maximization of the inter-habitat connectivity. The tree search methods branch-and-bound and multiobjective Monte Carlo tree search were designed specifically to solve the problems. The methods could be used as heuristics, as a time limit of 2 hours was imposed. All harvest scheduling problems were based on the socalled cluster formulation. The proposed models and methods were tested with sixteen real and hypothetical instances ranging from small to large. The results obtained for branch-and-bound and Monte Carlo tree search show that these methods were able to find solutions for all instances. The results suggest that it is possible to address the environmental restrictions with small reductions of the net present value. With respect to the forestry fragmentation caused by harvestings, the results suggest that, although clearcut size constraints tend to disperse clearcuts across the forest, compromising the development of large habitats, close to each other, the proposed models, with the other environmental constraints, attempt to mitigate this effect

Robust scheduling in forest operations planning

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.Includes bibliographical references (p. 67-68).Forest operations planning is a complex decision process which considers multiple objectives on the strategic, tactical and operational horizons. Decisions such as where to harvest and in what order over different time periods are just some of the many diverse and complex decisions that are needed to be made. An important issue in real-world optimization of forest harvesting planning is how to treat uncertainty of a biological nature, namely the uncertainty due to different growth rates of trees which affects their respective yields. Another important issue is in the effective use of high capital intensive forest harvesting machinery by suitable routing and scheduling assignments. The focus of this thesis is to investigate the effects of incorporating the robust formulation and a machinery assignment problem collectively to a forest harvesting model. The amount of variability in the harvest yield can be measured by sampling from historical data and suitable protection against uncertainty can be set after incorporating the use of a suitable robust formulation. A trade off between robustness to uncertainty with the deterioration in the objective value ensues. Using models based on industrial and slightly modified data, both the robust and routing formulations have been shown to affect the solution and its underlying structure thus making them necessary considerations. A study of feasibility using Monte Carlo simulation is then undertaken to evaluate the difference in average performances of the formulations as well as to obtain a method of setting the required protections with an acceptable probability of infeasibility under a given set of scenarios.by Lui Cheng, Lim.S.M

An integrated planning model for multi-supplier, multi-facility, multi-customer, multi-product and multi-period : application to the wood furniture industry

Typiquement, un réseau de création de valeur dans l'industrie du meuble en bois, est composé de fournisseurs de billes de bois, de scieries, de séchoirs, d'usines de meubles, de centres de distribution et de détaillants. Dans cette thèse, nous nous concentrons sur l'étude du réseau qui assure l'approvisionnement des usines de meubles en bois. La problématique à laquelle font face les entreprises de ce réseau se situe principalement au niveau de la synchronisation des flux de matière. Ces derniers doivent respecter les contraintes de capacité, de procédés, de transport et la diversité des produits, pour satisfaire la demande. La planification, dans ce contexte, repose sur une vision locale ce qui affecte la performance globale du réseau. L'objectif de cette thèse est de proposer un modèle de planification intégrée dans un contexte, multifoumisseurs, multiusines, multiproduits, multiclients et multipériodes, qui vise la synchronisation des flux, et la maximisation de la performance globale tout en respectant les différentes contraintes du réseau. Nous proposons un modèle générique du problème de planification intégrée qui permet de déterminer les décisions tactiques d'approvisionnement, d'inventaire, de flux de matière et de sous-traitance. Ce modèle est un programme linéaire mixte en nombres entiers de grande taille. Nous avons développé une heuristique basée sur la décomposition dans le temps qui exploite l'aspect multipériodes du problème de planification. Nous avons aussi proposé deux solutions basées sur la décomposition de Benders et la décomposition croisée pour réduire le temps de résolution. Enfin, ce modèle a été validé en utilisant les données réelles de l'entreprise partenaire du projet et les résultats, montrent des réductions potentielles du coût total des opérations de l'ordre de 22%. L'approche de planification intégrée adoptée ainsi que les méthodes de résolution proposées dans cette thèse peuvent être exploitées pour la planification des réseaux dans d'autres secteurs d'activités ayant des similarités avec la problématique traitée dans cette thèse

Transportation Optimization in Tactical and Operational Wood Procurement Planning

RÉSUMÉ : L'économie canadienne est dépendante du secteur forestier. Cependant, depuis quelques années, ce secteur fait face à de nouveaux défis, tels que la récession mondiale, un dollar canadien plus fort et une baisse significative de la demande de papier journal. Dans ce nouveau contexte, une planification plus efficace de la chaîne d'approvisionnement est devenue un élément essentiel pour assurer le succès et la pérennité du secteur. Les coûts de transport représentent une dépense importante pour les entreprises forestières. Ceci est dû aux grands volumes de produits qui doivent être transportés sur de grandes distances, en particulier dans le contexte géographique d'un grand pays comme le Canada. Même si les problèmes de tournée de véhicules sont bien couverts dans la littérature, le secteur forestier a beaucoup de caractéristiques uniques qui nécessitent de nouvelles formulations des problèmes et des algorithmes de résolution. À titre d’exemple, les volumes à transporter sont importants comparés à d’autres secteurs et il existe aussi des contraintes de synchronisation à prendre en compte pour planifier l'équipement qui effectue le chargement et le déchargement des véhicules. Cette thèse traite des problèmes de planification de la chaîne logistique d'approvisionnement en bois: récolter diverses variétés de bois en forêt et les transporter par camion aux usines et aux zones de stockage intermédiaire en respectant la demande pour les différents produits forestiers. Elle propose trois nouvelles formulations de ces problèmes. Ces problèmes sont différents les uns des autres dans des aspects tel que l'horizon de planification et des contraintes industrielles variées. Une autre contribution de cette thèse sont les méthodologies développées pour résoudre ces problèmes dans le but d’obtenir des calendriers d’approvisionnement applicables par l’industrie et qui minimisent les coûts de transport. Cette minimisation est le résultat d’allocations plus intelligentes des points d'approvisionnement aux points de demande, d’une tournée de véhicules qui minimise la distance parcourue à vide et de décisions d'ordonnancement de véhicules qui minimisent les files d’attentes des camions pour le chargement et le déchargement. Dans le chapitre 3 on considère un modèle de planification tactique de la récolte. Dans ce problème, on détermine la séquence de récolte pour un ensemble de sites forestiers, et on attribue des équipes de récolte à ces sites. La formulation en programme linéaire en nombres entiers (PLNE) de ce problème gère les décisions d'inventaire et alloue les flux de bois à des entrepreneurs de transport routier sur un horizon de planification annuel. La nouveauté de notre approche est d'intégrer les décisions de tournée des véhicules dans la PLNE. Cette méthode profite de la flexibilité du plan de récolte pour satisfaire les horaires des conducteurs dans le but de conserver une flotte constante de conducteurs permanents et également pour minimiser les coûts de transport. Une heuristique de génération de colonnes est créée pour résoudre ce problème avec un sous-problème qui consiste en un problème du plus court chemin avec capacités (PCCC) avec une solution qui représente une tournée de véhicule. Dans le chapitre 4, on suppose que le plan de récolte est fixé et on doit déterminer les allocations et les inventaires du modèle tactique précédent, avec aussi des décisions de tournée et d'ordonnancement de véhicules. On synchronise les véhicules avec les chargeuses dans les forêts et dans les usines. Les contraintes de synchronisation rendent le problème plus difficile. L’objectif est de déterminer la taille de la flotte de véhicules dans un modèle tactique et de satisfaire la demande des usines avec un coût minimum. Le PLNE est résolu par une heuristique de génération de colonnes. Le sous-problème consiste en un PCCC avec une solution qui représente une tournée et un horaire quotidien d'un véhicule. Dans le chapitre 5, on considère un PLNE du problème similaire à celui étudié dans le chapitre 4, mais dans un contexte plus opérationnel: un horizon de planification d'un mois. Contrairement aux horaires quotidiens de véhicules du problème précédent, on doit planifier les conducteurs par semaine pour gérer les situations dans lesquelles le déchargement d’un camion s’effectue le lendemain de la journée où le chargement a eu lieu. Cette situation se présente quand les conducteurs travaillent la nuit ou quand ils travaillent après les heures de fermeture de l'usine et doivent décharger leur camion au début de la journée suivante. Ceci permet aussi une gestion plus directe des exigences des horaires hebdomadaires. Les contraintes de synchronisation entre les véhicules et les chargeuses qui sont présentes dans le PLNE permettent de créer un horaire pour chaque opérateur de chargeuse. Les coûts de transport sont alors minimisés. On résout le problème à l’aide d’une heuristique de génération de colonnes. Le sous-problème consiste en un PCCC avec une solution qui représente une tournée et un horaire hebdomadaire d’un véhicule.----------ABSTRACT : The Canadian economy is heavily dependent on the forestry industry; however in recent years, this industry has been adapting to new challenges including a worldwide economic downturn, a strengthening Canadian dollar relative to key competing nations, and a significant decline in newsprint demand. Therefore efficiency in supply chain planning is key for the industry to succeed in the future. Transportation costs in particular represent a significant expense to forestry companies. This is due to large volumes of product that must be transported over very large distances, especially in the geographic context of a country the size of Canada. While the field of vehicle routing problems has been heavily studied and applied to many industries for decades, the forestry industry has many unique attributes that necessitate new problem formulations and solution methodologies. These include, but are not limited to, very large (significantly higher than vehicle capacity) volumes to be transported and synchronization constraints to schedule the equipment that load and unload the vehicles. This thesis is set in the wood procurement supply chain of harvesting various assortments of wood in the forest, transporting by truck to mills and intermediate storage locations, while meeting mill demands of the multiple harvested products, and contributes three new problem formulations. These problems differ with respect to planning horizon and varied industrial constraints. Another contribution is the methodologies developed to resolve these problems to yield industrially applicable schedules that minimize vehicle costs: from smarter allocations of supply points to demand points, vehicle routing decisions that optimize the occurrence of backhaul savings, and vehicle scheduling decisions that minimize queues of trucks waiting for loading and unloading equipment. In Chapter 3, we consider a tactical harvest planning model. In this problem we determine the sequence of the harvest of various forest sites, and assign harvest teams to these sites. The MILP formulation of this problem makes inventory decisions and allocates wood flow to trucking contractors over the annual planning horizon, subject to demand constraints and trucking capacities. The novel aspect of our approach is to incorporate vehicle routing decisions into our MILP formulation. This takes advantage of the relatively higher flexibility of the harvest plan to ensure driver shifts of desired characteristics, which is important to retain a permanent driver fleet, and also prioritize the creation of backhaul opportunities in the schedule. A branch-and-price heuristic is developed to resolve this problem, with the subproblem being a vehicle routing problem that represents a geographical shift for a vehicle. In Chapter 4, we assume the harvest plan to be an input, and integrate the allocation and inventory variables of the previous tactical model with vehicle routing and scheduling decisions, synchronizing the vehicles with loaders in the forests and at the mills. The synchronization constraints make a considerably more difficult problem. We use this as a tactical planning model, with no specific driver constraints but a goal of determining vehicle fleet size to maximize their utilization. The objective is to meet mill demands over the planning horizon while minimizing transportation and inventory costs, subject to capacity, wood freshness, fleet balancing, and other industrial constraints. The MILP formulation of the problem is resolved via a column generation algorithm, with the subproblem being a daily vehicle routing and scheduling problem. In Chapter 5, we consider a similar problem formulation to that studied in Chapter 4, but set in a more operational context over a planning horizon of approximately one month. Unlike the daily vehicle schedules of the previous problem, we must schedule drivers by week to manage situations of picking up a load on one day and delivering on another day, which is necessary when drivers work overnight shifts or when they work later than mill closing hours and must unload their truck on the next day's shift. This also allows for more direct management of weekly schedule requirements. Loader synchronization constraints are present in the model which derives a schedule for each loader operator. Given mill demands, transportation costs are then minimized. We resolve the problem via a branch-and-price heuristic, with a subproblem of a weekly vehicle routing and scheduling problem. We also measure the benefits of applying interior point stabilization to the resource synchronization constraints in order to improve the column generation, a new application of the technique

An optimization and simulation framework for integrated tactical planning of wood harvesting operations and lumber production

La planification tactique des opérations forêt-usines est centrée sur trois éléments principaux : la récolte, le transport et la transformation du bois. La planification de cette chaine d’approvisionnement est très complexe. Il existe déjà des outils pour faciliter la décision de décideur tels que FPInterface et Optitek, tous deux développés par FPInnovations. Cette mémoire vise à développer un module d’optimisation qui est connecté aux utiles de simulation. LogiOpt est constituée d'un modèle mathématique. Le modèle développé vise l’optimisation de la chaîne d’approvisionnement entre la forêt et l’usine en concentrant les efforts sur les activités que l’entreprise planifie conjointement avec son entrepreneur d’opérations forestières principal. Grâce à ces solutions de logiciels de simulation et de notre modèle mathématique, nous combinons à la fois dans notre cadre récolte, le transport, l'allocation des bois et des opérations de production. Pour tester notre model mathématique, nous avons utilisé les données d’une année d’exploitation à une entreprise québécoise œuvrant dans le milieu forestier. Nous avons comparé nos résultats avec un plan tactique manuel « simulé ». De ce fait, nous avons constaté que LogiOpt effectue une meilleure allocation de la matière première en allant récolter dans moins de blocs de récolte tout en utilisant des bois ayant un meilleur rendement en usine. Conséquemment, on produit plus de produits finis en usine tout en utilisant la même quantité de bois qu’un plan tactique plus traditionnel.Forest and sawmills tactical planning is based on three main elements: wood harvesting, wood transportation and wood transformation. Planning the whole supply chain, is quite complex. Tools have been built to help manager in his decision process, for example FPInterface and Optitek, which were developed by FPInnovations. The aim of this thesis is to develop an optimization module, LogiOpt, which will be integrated to simulation tools. LogiOpt is made of a mathematical model. The developed model aims at optimizing the supply chain between the forest and the mills. Using simulation software solutions and our mathematical model, we combine at the same time in our framework harvesting, transportation, wood allocation and production operations. To test our mathematical model, we used data obtained from one business year of a Quebec based wood manufacturer. We compared our results with a manual simulated tactical plan. In this regard, we observed that LogiOpt performs better in wood allocation between sawmills, harvesting in less harvesting while using wood with better output. We then end up producing more finished products at sawmills using the same wood quantity as a traditional tactical plan

Road-network location heuristics for the tactical harvest-scheduling model

In tactical planning in hierarchical forest management, cut-blocks are selected for maximizing revenue and road networks are allocated at minimal cost in order to maximize profit. The selected cut-block set and requisite road-network, connecting the cut-blocks, therefore have an interdependent relationship. The location of these two elements in tactical planning must therefore be considered simultaneously in a tactical harvest-scheduling model. This integration presents a major computational challenge, especially with regard to the execution time required to find an optimal solution to the tactical harvest-scheduling model. The objective of this thesis isto explore the influence of different road location heuristics, used within the tactical harvest scheduling model, upon the model’s execution time and solution quality. We nested the three different types of roadlocation heuristics within the harvest-scheduling model in order to evaluate their effectiveness by three criteria: execution time, road construction cost and objective function value. In addition, after the tactical model was run, we executed and evaluated the usefulness of a road network repair algorithm, designed to improve further the solution of the road-network location generated by the tactical harvest-scheduling model. The thre heuristics were evaluated on a real-world dataset, representing a section of the Kenogami forest in Ontario, Canada. Our result show: i) that the Shortest Path Origin Heuristic (SPOH) achieved the fastest execution time and lowest construction cost when integrated within the tactical harvest-scheduling model; and ii) that the road network repair algorithm successfully lowered the road network costs and thereby increased the objective function value of all solutions generated using the tactical planning model. These results are significant for two reasons: first, they show that the choice of the road network heuristic used within a tactical planning model can have a major influence on the model’s solution quality; and second, that the use of a road repair algorithm, on the solution generated using a tactical model, is of major economic value in forest management planning