Abstract
Our purpose was to study the efficient planning of the specifications for forest road systems. The decision model for these specifications were composed by three cost functions, namely construction, repairs and maintenance costs, land costs, and wood transportation costs. The relationship between forest-road length and the forest area being exploited which is similar to HACK's law on geography was applied to the measuring of wood transportation volume. The results showed that forest roads, which have the character of public roads in Japan, are needed to plan exploited forest areas of more than several hundreds of hectares. Therefore, low-structure forest roads for only forestry use would be needed. Main skidding roads for tractor and forwarder uses can be constructed on a large scale in terms of terrain slopes and wood volume conditions.
