A study of the relationships between haul truck speed and road geometry with considerations to load status and engine power for primary forest roads in Northern Saskatchewan

Abstract

This report presents an analysis of haul truck speed with respect to: 1) road geometry, 2) load status, and 3) engine power for primary forest roads in northern Saskatchewan. The investigations were completed with data collected from a working global positioning system based monitoring system designed to track haul truck speeding violations and wood movement for Weyerhaeuser's log haul centred in Prince Albert, Saskatchewan. Four sections of road were utilized for the analysis; characterized by: 1) rolling hills with a positive net change in elevation, 2) rolling hills with no net change in elevation, 3) rolling hills with a negative net change in elevation, and 4) flat. Each section represents the typical geometric characteristics found with the primary forest roads of northern Saskatchewan. Truck speeds were recorded and analysed for empty and loaded conditions. Two trucks characterized by a six -axle tridem configuration were utilized in the study. One truck was powered by a 425 hp power plant, the other, by a 500 hp power plant. The results obtained from the study indicated very little differences in average haul truck speed as a result of differing road geometry while travelling empty. Load status had the greatest impact on the average speeds observed by loaded haul trucks travelling over the rolling sections of road. Average speeds of loaded haul trucks can be expected to differ from 1.3 kmlhr to 10.8 km/hr when compared to average speeds across flat sections. Load status appeared to have no effect on speed across the flat section. Increased engine power indicated no advantages with respect to average speed when travelling loaded. Higher average speeds for the 500 hp truck indicate a that 1.5 km/hr to 5.2 km/hr increase in average speed can be expected across the rolling sections when travelling empty. Deviations in the observed average speeds indicated that average speeds will vary more over rolling sections of road; supporting others findings that increased gradient accelerates road deterioration. Higher standard deviations for loaded trucks also indicate that loaded trucks may be more susceptible to changing operating conditions, such as road roughness. The effect of a net change in elevation was not demonstrated. The enforced speed limit of 80 kmlhr appeared to be a limiting factor in achieving higher speeds for the haul trucks. The major shortfalls of the project appear to be with the inaccuracy and gaps with the truck speed data. It is also recommended that more variable terrain be considered for future projects. Key Words: forest road, geometric design, haul truck performance prediction, global positioning system