Theoretical Potentials of Forwarder Trailers with and without Axle Load Restrictions

In mechanized ground-based forestry, machines operate on rough soils that, ideally, should remain unaffected by the operation. This implies small (that is, light) loads and careful driving are required. However, economical rationality implies large loads and high speeds. Recently, the concept of adding a trailer to a conventional forwarder has been revived, with the objective of addressing both concerns, and fitting into the current, mechanized, cut-to-length system. Here we present the theoretical benefits of the forwarder-trailer concept compared to conventional forwarding for final-felling operations. The analysis addresses the trailer potential in terms of break-even extraction distances under different scenarios, and estimates the abundance of favorable conditions (as a percentage of final-felling volume) in Swedish final fellings. The results show that the forwarder-trailer concept has potential to reduce costs, and especially if there are restrictions on axle loads. However, the viability of the trailer concept is highly sensitive to changes in the increased purchase costs and the increased work-element time-consumption. That is, small changes in these variables result in large changes in viability. In the scenarios presented here, the increase in time consumption was more influential than the purchase cost. It can be concluded that there are potential economic and possibly also environmental benefits that warrant further investigation of the forwarder-trailer concept, which is currently being evaluated in practice in Sweden.