Optimization Models for Forest Road Upgrade Planning |
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Authors: | Mathias Henningsson Jenny Karlsson Mikael Rönnqvist |
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Institution: | 1.Division of Optimization,Link?ping University,Link?ping,Sweden;2.Department of Finance and Management Science,Norwegian School of Economics and Business Administration,Bergen,Norway;3.The Forestry Research Institute of Sweden,Uppsala,Sweden |
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Abstract: | Road blocking due to thawing or heavy rains annually contribute to a considerable loss in Swedish forestry. Companies are
forced to build up large stocks of raw material (saw and pulp logs) in order to secure a continuous supply when access to
the road network is uncertain. Storage outdoors leads to quality deterioration and monetary losses. Other related costs due
to road blocking are road damage and longer haulage distances. One approach to reduce the losses due to road blocks is to
upgrade the road network to a standard that guarantees accessibility. We consider the road upgrade problem from the perspective
of Swedish forest companies with a planning horizon of about one decade. The objective is to minimize the combined upgrade
and transportation costs. We present two mixed integer programming models, which are uncapacitated fixed charge network flow
problems including multiple assortments, several time periods and a set of road classes. One model is based on arc flows and
one on route flows. For a typical planning instance, the models become large and we propose how to improve solution performance
through model strengthening. The models are tested in a case study for a major Swedish forest company.
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Keywords: | forestry wood flow road upgrading practice of OR modelling integer programming model strengthening |
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