Forestry transport expenditures in Australia include both the costs of owning and operating logtrucks, and the costs of constructing and maintaining many kilometres of logging roads. Therefore,improving transport efficiency requires consideration of both road and truck related factors. However, analysis of these factors involves many complex interacting variables. A computer simulation model, TRUCKSIM, has been developed to assist in these analyses by predicting the effects of both road and alternative vehicle specification on transport performance. A description of the model and it's supporting programs is presented, together with a discussion of it's limitations and examples of it's use in evaluating alternative truck and road specifications