Haulage trucking comprises between 50%, and higher amounts of the total costs incurred during surface mining. Haul road infrastructure is an important production resource that determines the overall safety, cycle time, lifespan of machines, and cost per ton of materials moved. Traditional approaches in haul road design often result in early failure, high equipment wear, and higher operating costs. Integrated design of haul roads includes four mutually dependent design elements, which are geometric design, structural design, functional design, and maintenance design. Effective consideration of all the elements results in cost-effective mining infrastructure.
The geometric design determines the haul road physical alignment in horizontal and vertical directions. Optimal longitudinal slopes are between 8% and 10% for traditional rigid body haul trucks. Steeper longitudinal slopes beyond 10% significantly reduce haul truck speed, increase diesel fuel consumption, and also stress drive trains and retarders. Consistent slopes are mandatory because sudden changes in slope result in unnecessary shifting of gears in the transmission and overheating of retarders. The recommended road width for two lanes is at least 3.5 times the vehicle size, and 2% to 3% crown or cross slope ensures proper drainage of the road.
The structural design determines the strength of pavement needed to withstand heavy wheel loads without any subgrade distress. Unsurfaced mine haul roads use multilayered structures that consist of a prepared subgrade, a layer of selected blasted waste rock and 200 mm wearing course. The appropriate base layers have hard and blocky waste rock with a maximum aggregate size of two-thirds of the thickness of the base layer. The functional design controls the selection of wearing course material to reduce road wear and rolling resistance. The most suitable wearing course gravels include well-graded crushed aggregate mixed with bind fines to prevent dusting and ravelling.
Rolling resistance is the term used to define extra forces that act against movement of a vehicle and are expressed as percentages of gross vehicle weight. A one percent rise in rolling resistance decreases truck speed in ramps by 10-13%, and by up to 26% in level road sections. Mine sites studies indicate that lowering rolling resistance from 6% to 2% decreases haul cycle times by 21% and reduces fuel used per cycle by 19%. Blading and watering in controlled amounts (0.5 liters per square meter) and dust suppressants maintain road surface quality and protect costly haul tires.
| Design Component | Key Engineering Focus | Primary Operational Benefit |
| Geometric Design | Vertical gradients (8-10%), road width (3.5x vehicle width), and cross-slope (2-3%) | Optimized cycle times, safe sight distances, and effective water shedding |
| Structural Design | Subgrade compaction and selected blasted waste rock base layer thickness | Prevention of subgrade rutting, layer deformation, and structural collapse |
| Functional Design | Wearing course selection (-40mm aggregate with 5-20% fines binder) | Reduced rolling resistance, improved skid resistance, and minimal dust |
| Maintenance Design | Scheduled blading, light watering (0.5 L/m²), and dust palliative treatment | Lower fuel consumption, reduced tire damage, and extended road service life |
Well-designed haul roads turn transport routes from mine liabilities to high performing mines assets. Good alignment, strong construction layers and rolling resistance control improve haul cycle times, decrease diesel fuel usage, and safeguard capital equipment. This is how mine operators maximize fleet performance and save money.
