Designing the forest road network is a complex and specialized process which include; route selection, field investigation, data analyzing, and finally determine the best variant, which more accommodate with site-specific road locations. Present study was designated to evaluate the existing forest road network and to development of the existing forest road network in the mountainous forests, northern Iran (Savadkoh district). In order to conduct the study firstly, the effective environmental factors such as; slope, aspect and elevation layers, were identified to find appropriate options for road routing. In the next step, the Geographic Information System (GIS) was applied to evaluate and develop an existing forest road network. The length and density of the existing road network are by about 1.75 km and 10.14 m.ha-1, respectively. The new variant was developed with regard to forest conditions and physiographic conditions using PEGGER software. The length and density of new variant road were 1.38 km and 8 m.ha-1, respectively. The development of the existing road network has been increased the total road density from 10.15 to 18.16 m.ha-1 and also could cover 55.5% of forest area for timber harvesting operations. Approximately, 32.14% total length of the new variant was passed on 15-30% slope and 64% of the new variant was passed on 30-60% slope terrains, which is more likely to be minimal negative environmental impact. Moreover, the new variant has had a better perform than existing road. The results showed that this method can be more helpful and road network can be designed quickly with less cost than traditional method. As well as confirmed that application of this system in such level by the computer analysis can be effective in preparation of the optimum routes designed plans.
