Hyrcanian forest is the only forest designated for commercial timber production in Iran. Ground-based skidding is the most common extraction system used in the forest, though large parts of the forest are still inaccessible due to the low road density (1-2 m ha-1). To facilitate timber harvesting in the forest, it has been proposed to increase the road density up to 20 m ha-1. The aim of this study was to incorporate the estimated skidding costs through a time study into an existing transportation planning tool, NETWORK 2000, to help decision making on forest road building. We applied this method to the Gorazbon district in the Hyrcanian forest, where 244 links were built for the analysis. The best solution found by NETWORK 2000 indicates that all the proposed roads should be built to minimize the total skidding and road building cost