Speaker
Description
Two-stage trucking systems are increasingly used in steep-land harvesting in Aotearoa New Zealand to reduce the need for the quality of roading and landings required to allow access for on-highway high productivity motor vehicles (HPMV’s). In these systems, stems or processed logs are trans-shipped between a constrained extraction/processing landing and a larger storage and load-out skid using a dedicated intermediate truck. This study synthesises elemental time study findings from nine two-stage systems based on eight different intermediate truck configurations, spanning two widely used platform types: (1) modified 6WD articulated dump trucks, and (2) off-highway/on-highway log trucks (6x8 and 8x8). Data were collected across multiple harvesting contexts (ground-based and cable), with cycle elements separated into loading, travel loaded, unloading, travel unloaded, and delays. Intermediate road distance and grade were measured in segments, and payloads were estimated using truck scales or log-count/volume methods.
Across case studies, haul distances ranged from 350 m to 5,440 m, with average loaded speeds typically between 2 and 7 m/s depending on road profile and surface condition. Productivities ranged from 19 to 44 tonnes per productive machine hour (t/PMH), with utilisation 73–96%. Results indicate that intermediate-truck productivity is primarily determined by (i) haul distance and road profile, (ii) effective payload capacity (including the ability to use a trailer and the degree of load sorting), and (iii) loading/unloading system design—particularly access to loaders and interference with other landing/skid activities. Where long haul distances combined with constrained payload (e.g., inability to use a trailer), travel time became dominant and reduced throughput, sometimes requiring additional truck hours to avoid bottlenecking the prime mover. Conversely, higher payload capacity and/or shorter leads could offset challenging grades, and well-integrated landing/skid layouts reduced interference delays.
These findings support a practical design implication for harvest planners: intermediate trucking should be treated as a system component whose performance is jointly shaped by truck configuration, road geometry, loader availability, and landing/skid layout, rather than by truck platform alone. When these elements are aligned, two-stage trucking can provide access to steep or erosion-prone settings while potentially maintaining or improving overall harvesting productivity and reducing safety and environmental risk.
| Keywords | two-stage; trucks; productivity; steep-lands |
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