Two-stage trucking using modified dump trucks

Authors: Trevor Best and Rien Visser
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2024, Issue N.Z.J.For. 69(3) 2024, pp Pages 28 - 35, Nov 2024
Publisher: New Zealand Institute of Forestry

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Abstract: Two-stage’ trucking uses an intermediate extraction system between the primary extraction system pulling stems from the cutover and the loading out of logs. While this additional step adds complexity and costs, if well planned, two-stage trucking can provide benefits that could make it worth considering as an alternative to the more traditional ‘one-stage’ system. It can reduce environmental impacts by reducing the need for larger landings in steep terrain. It can also save on infrastructure costs through lower standard roading and by dephasing the loading activity can create an opportunity for increased productivity and safety. Many variations of two-stage systems exist, but one lower cost option is using modified dump trucks to move processed logs to the sort, storage and load-out skid. Limited information is available about the productivity of two-staging, although such information is required to balance the overall efficiency of the harvesting system. Time and motion studies were completed on three different existing operations, all using modified 6 wheel-drive (6WD) dump trucks capable of carrying over 20 tonne payloads. In addition to timing all the elements of the round-trip, road length and grade were measured in segments, and payloads were estimated through logs counts and average log volumes. Results include average speeds from 9 to 15 km/hr, with the truck slowed both going up and downhill. Average delay-free cycle times ranged from 15.9 to 24 minutes. Loading times (range 6.2 to 15.3 minutes) and haul distance (range 350 to 1,265 m) appeared to have the greatest impact on cycle times, with the resulting productivity ranging from 34 to 44 tonnes per productive machine hour. The operations studied appeared to be very well integrated with an average utilisation rate of 75% across all three trucks, achieving a good result for the contractor and forestry companies. Each variation of the two-stage approach has its costs and implementation challenges, and yet can also offer advantages as demonstrated in this case study.

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