Designation of timber extraction routes in a GIS using road maintenance cost data

The Arc View® network analyst program was used to designate timber transportation routes on the basis of shortest distance, and road maintenance costs for a sample forest access road network in Ireland. Road sections were costed separately on the basis of measured transient pavement surface deflections and attribute information. Direct cost comparisons of 76 origin-to-destination (o-d) route pairs were made for 4 seasonal conditions. It was found that 46 percent of the current designated transportation routes (o-d pairs) were also the optimum (shortest distance routes). The unit cost associated with maintenance of the optimum route networks was found to be higher (10,969 $/km) than those associated with the designated haulage routes (10,567 $/km). It was also found that an increase in the proportion of lower standard roads in the network increased the unit maintenance costs by 332 $/km. Therefore, timber transportation should be routed to the nearest higher-class roads to minimize the associated expenses on road maintenance. Restrictions could be imposed on timber movement through roads with width, gradient, and vertical-clearance restrictions, and sections with inherent seasonal structural weaknesses. The described method can be used to rapidly assess routing alternatives with respect to shortest transportation paths and inherent road conditions, or in avoidance of road pavement, environmental, and public liability constraints.