Effect of Trail Condition, Slope, and Direction of Extraction on Forwarding Performance: Insights from a Controlled Comparative Study

The performance of timber harvesting equipment is important for local operational planning and for making decisions on the way in which the forests should be opened up. However, there are many options used to extract timber, and there is a high variability in their performance. Forwarding is commonly used and became an attractive option for low-access forests. A controlled experiment was set up in this study to see how the configuration of the trails, characterized in terms of slope and surface condition, and the extraction direction (uphill or downhill) may affect the performance of forwarding operations. GNSS (Global Navigation Satellite System) data were collected at a rate of 5 s for five replications of moving empty downhill and uphill, respectively, on a dirt trail, measuring 250 m in length and having a slope of about 11%. The same experiment was run with the machine loaded at full capacity, then four replications with the machine loaded and unloaded moving downhill and uphill, respectively, were performed on a forest road resembling a rocky trail, which measured 390 in length and had a slope of about 4%. GNSS data were used to extract the moving speed for all the tested conditions with the aim to compute the cycle time, and the payload volume estimate was used to estimate efficiency, and productivity, depending on extraction distance in a range of 50 to 1000 m. For the first trail, statistical comparison tests indicated significant differences in the speed of uphill and downhill movement, for both empty and loaded conditions, whereas for the second trail, there were no significant differences in speed. In addition, on the second trail, the sustained speed was almost double. These were reflected sharply in the cycle time, efficiency, and productivity, depending on extraction distance and trail condition. These findings are important for decision making on local operational planning and forest opening up.