The forest harvesting is a most expensive system in forest management plans. The main objective of the harvesting is to minimize logging time, cost and damage. In order to correct management and minimize cost, all of the components of a system must be recognized. Primary transportation is a component of harvesting system, which is carried out using rubber-tired skidders and skid trails in Iran. Cross slope of skid trails is one of the effective factors on skidding time. In this study, the effects of the cross slope of skid trail on skidding time for loaded and unloaded skidder was investigated. After measuring the effective factors on skidding time, data were analyzed in SPSS software and then models were produced. Results showed that skidding time was a function of cross slope, number and volume of pieces. For unloaded skidder, the relation between cross slope and skidding time was incremental and for loaded skidder the relation between cross slope and skidding time was multiplier parabola. The skidding time increased with increasing the volume of pieces in all cross slope classes.
