A computer model to differentiate skidder and cable-yarder based road network concepts on steep slopes

Road spacing on slpes depends on the underlying off-road transportation technology. One major decision in road network planning is to determine under what terrain conditions ground- or cable based extraction systems should be applied. The present investigation aims to develop a road spacing model for steep slope conditions and to implement a total cost model for skidder and cableyarder based road network concepts. The study analyzes transportation and road geometry to specify the relationship between road density, slope gradient, and road spacing. Production functions for skidder and yarder-systems make it possible to derive transportation cost as a function of road density and slope gradient. A total cost function integrates road building cost, harvesting strategy, and production economics to derive optimal road density for the two network concepts. The difference between the cost levels at optimum road density is an indicator for differentiating cable and skidder-based extraction systems. The model was implemented as a Visual Basic add-in for Microsoft Excel spreadsheet software. This flexible approach makes future adaptations and changes very easy due to the modular concept. The validity of the model is limited to the production functions of the underlying off-road transportation technologies. Future work needs to develop production functions for the state-of-the-art technologies and to improve the road building cost mode