The goals of the study were to develop comprehensive productivity models of skidders for the Hyrcanian forest areas of Iran and to compare the productivities of two existing skidding machine types in order to select the most profitable ones under various operating conditions. Estimating productivity of forest equipment is imperative for forest managers to estimate production costs of logging and for developing a cost efficient logging plan. This paper deals with the performance of ground based harvesting systems (tracked and wheeled skidders) in the mountainous forest of the northern part of Iran. Two regression models for each skidding machine type (one equation for uphill and another for downhill skidding) were developed. In addition, related times for each element of skidding cycle and delay times were determined.
