🎓 Lesson 1
D1
Getting Started with Freight Cost Optimization
Freight cost optimization is finding the most efficient way to move mined materials from the pit to processing or shipping points while spending the least amount of money.
🎯 Learning Objectives
- ✓ Calculate freight cost per tonne-kilometer for a given haul cycle
- ✓ Analyze the impact of payload utilization and rolling resistance on total haul cost
- ✓ Design an optimized truck-trailer configuration for a specified ore throughput and haul distance
- ✓ Apply empirical resistance models to estimate fuel and tire wear costs
- ✓ Explain how haul road grade and surface condition influence lifecycle freight cost
📖 Why This Matters
In open-pit mining, haulage typically accounts for 35–50% of total operating costs — more than drilling, blasting, or loading combined. A 5% reduction in freight cost per tonne can improve project NPV by millions over a mine’s life. For blasting engineers, understanding freight optimization ensures blast designs support efficient loading and hauling — e.g., proper fragmentation reduces rehandling, avoids oversized boulders that slow trucks, and improves payload consistency. Ignoring this link risks suboptimal blast patterns that look good on paper but inflate haulage costs in practice.
📘 Core Principles
Freight cost optimization rests on three interdependent pillars: (1) Vehicle dynamics — governed by engine power, gross vehicle weight, rolling resistance, and grade resistance; (2) Operational efficiency — driven by cycle time components (load, haul, dump, return), availability, and utilization; and (3) Cost structure — comprising fixed costs (depreciation, insurance), semi-variable costs (maintenance, tires), and variable costs (fuel, labor). Optimization requires recognizing trade-offs: larger trucks reduce unit cost at long haul distances but increase capital outlay and require wider roads; higher payloads improve tonne-km efficiency but may compromise safety or exceed axle limits. Real-world optimization also incorporates stochastic factors — traffic congestion, weather delays, and equipment breakdowns — modeled via discrete-event simulation or Monte Carlo analysis.
📐 Total Freight Cost per Tonne-Kilometer
This foundational formula aggregates all major haulage cost drivers into a normalized metric enabling comparative analysis across fleets, routes, or scenarios. It is used during mine planning, fleet acquisition studies, and continuous improvement reviews.
Total Freight Cost per Tonne-Kilometer (Cₜₖ)
Cₜₖ = (C_fuel + C_tire + C_maint + C_labor + C_fixed) / (Payload × Haul Distance)Normalizes total haulage cost to enable comparison across configurations, distances, and materials.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| Cₜₖ | Freight cost per tonne-kilometer | $/t·km | Normalized economic metric for haulage efficiency |
| C_fuel | Fuel cost per cycle | $ | Diesel or alternative fuel cost for one complete haul cycle |
| C_tire | Tire cost per cycle | $ | Prorated tire replacement cost based on hours-of-service life |
| Payload | Loaded mass | tonnes (t) | Net payload carried per cycle (excluding tare weight) |
| Haul Distance | One-way loaded haul distance | kilometers (km) | Distance traveled while carrying payload |
Typical Ranges:
Large off-highway truck (>200 t payload), <3 km haul: $0.025 – $0.035/t·km
Medium rigid truck (40–60 t), steep access ramp (>8% grade): $0.045 – $0.070/t·km
💡 Worked Example
Problem: A 930E haul truck operates on a 4.2 km round-trip haul cycle (2.1 km one-way) with average grade of 6%, rolling resistance of 2.5%, payload of 220 t, cycle time of 18.4 min (0.307 hr), fuel consumption of 68 L/100 km, diesel price $1.25/L, tire cost $120,000/tire (life = 18,000 hrs), and maintenance cost $22/hr. Calculate Cₜₖ.
1.
Step 1: Compute tonne-kilometers per cycle = payload × haul distance = 220 t × 2.1 km = 462 t·km
2.
Step 2: Compute fuel cost per cycle = (68 L/100 km × 4.2 km) × $1.25/L = (2.856 L) × $1.25 = $3.57
3.
Step 3: Compute tire cost per cycle = ($120,000 / 18,000 hr) × 0.307 hr = $2.05
4.
Step 4: Compute maintenance cost per cycle = $22/hr × 0.307 hr = $6.75
5.
Step 5: Sum direct variable costs per cycle = $3.57 + $2.05 + $6.75 = $12.37
6.
Step 6: Compute Cₜₖ = $12.37 / 462 t·km = $0.0268/t·km
Answer:
The result is $0.0268 per tonne-kilometer, which falls within the safe range of $0.020–$0.035/t·km for large off-highway trucks in well-maintained hard-rock operations.
🏗️ Real-World Application
At BHP’s Mt. Arthur Coal Mine (Australia), engineers redesigned haul routes and adjusted bench pushbacks after discovering that 12% of total haulage cost stemmed from excessive grade-related speed reductions and gear-shifting losses. By lowering maximum grade from 10% to 7.5% on a critical 3.8 km segment—and optimizing blast fragmentation to ensure consistent 80% passing 300 mm—cycle time decreased by 14%, payload utilization increased from 89% to 96%, and Cₜₖ dropped from $0.032 to $0.024/t·km. This yielded $18.7M annual savings across the 42-truck fleet, validated using Fleet Management System (FMS) telematics data and verified via ISO 50001 energy audit protocols.
🔧 Interactive Calculator
🔧 Open Freight Cost Optimization Calculator📋 Case Connection
📋 Freight Cost Optimization in Large-Scale Industrial Projects
Complex engineering requirements at scale
📋 Small-Scale Freight Cost Optimization Implementation
Limited resources and tight budget
📋 Freight Cost Optimization in Challenging Environments
Environmental and terrain challenges
📋 Cost Optimization in Freight Cost Optimization
Maintaining quality while reducing costs