The formula
Cost per tonne = fleet cost per day ÷ tonnes moved per day
Fleet cost is usually built up from hourly rates. On wet hire, the rate includes the operator. On dry hire, you add the operator yourself. Check whether fuel is included, and add any costs that sit outside the rates, such as supervision, a water cart or haul road maintenance.
Worked example
This uses the same job as our haul cycle time example: a 2.4 km haul, one loader, four 25 t trucks and a 10-hour shift. The rates are made up for the arithmetic:
- Four trucks at $150 an hour and a loader at $220 an hour: $820 an hour
- Over 10 hours: $8,200 a day
- On a dry day the fleet moves 111 loads × 25 t = 2,775 t
Cost per tonne = $8,200 ÷ 2,775 t = $2.95 per tonne.
What a wet day costs
In the wet, the same fleet drops to 101 loads, or 2,525 t. The fleet costs the same for the day, so the cost per tonne rises to $8,200 ÷ 2,525 t = $3.25 per tonne, almost 10% more. Over a job with many wet days that adds up, which is why wet weather belongs in the rates as well as the program.
The cheapest rate per tonne isn't always the cheapest job
On a dry day, four trucks are slightly more than the loader can keep busy. Drop to three and the fleet costs $670 an hour, or $6,700 a day. It moves 94 loads × 25 t = 2,350 t, so the cost per tonne falls to $6,700 ÷ 2,350 t = $2.85 per tonne.
That looks cheaper, but the fleet now moves 425 t a day less, so the job takes about 18% longer. Every extra day carries time-related costs that aren't in the haul rate, such as supervision, site facilities, traffic management and the program itself. Compare whole-job costs, not just the rate per tonne.
Getting it right
- Use the production the fleet will really achieve, from the cycle time and the loader limit, not the trucks' best case
- Price wet days, night shifts and longer hauls separately if they apply
- Keep the rates current, and say what they include
- Test the sensitivity: change speeds, payloads and fleet size, and see how far the cost per tonne moves
The rates and figures here are assumptions for the arithmetic, not market rates.
Seeing it
If your haulage spreadsheet already does this, we can turn it into a 3D visual that runs on your numbers, so you can change a speed or a fleet size and show your client what happens.