What makes up a cycle
A truck's cycle is everything it does between one load and the next:
- Spot: positioning at the loader
- Load: the loader filling the truck
- Haul: travelling loaded to the dump
- Dump: manoeuvring and tipping
- Return: travelling empty back to the loader
- Queue: any time spent waiting for the loader
Travel time is distance divided by average speed: minutes = distance (km) ÷ speed (km/h) × 60. Use the average you'd expect over the whole run, not the truck's top speed. Accelerating, corners, grades, speed limits and the road surface all pull the average down.
Worked example: a dry day
A 2.4 km haul, one loader, and four trucks each carrying 25 t. The times and speeds are assumptions for the example:
- Spot 0.5 min, load 4.0 min, dump 1.5 min
- Haul loaded at an average of 25 km/h: 2.4 ÷ 25 × 60 = 5.76 min
- Return empty at an average of 35 km/h: 2.4 ÷ 35 × 60 = 4.11 min
The cycle is 0.5 + 4.0 + 5.76 + 1.5 + 4.11 = 15.87 min.
From cycle time to loads per day
Nobody works a full 60 minutes in every hour. A common allowance is a 50-minute productive hour, which covers short stops, waiting and small delays. On that basis:
- Loads per truck per hour: 50 ÷ 15.87 = 3.15
- Over a 10-hour shift: 31.5 loads per truck
- Four trucks could do 126 loads a day
Check the loader
The loader can only fill one truck at a time. Each truck spends 4.5 minutes at the loader (spot plus load), so the loader can manage at most 50 ÷ 4.5 = 11.1 loads an hour, or 111 loads in the 10-hour shift.
The trucks could do 126, but the loader caps it at 111. This fleet is loader-limited, and the trucks will spend some time queuing. A quick way to size the fleet is cycle time ÷ time at the loader: 15.87 ÷ 4.5 = 3.5 trucks keeps the loader busy. Three trucks would leave the loader waiting, at 94 loads a day. Four keep it working, with a little queuing.
A wet day
Rain on an unsealed haul road slows everything down. Say the averages drop to 18 km/h loaded and 25 km/h empty:
- Haul 8.00 min and return 5.76 min, so the cycle becomes 19.76 min
- Loads per truck: 50 ÷ 19.76 = 2.53 an hour, or 25.3 a shift
- Four trucks: 101 loads a day
Now the loader could do 111 but the trucks only deliver 101. The fleet has become truck-limited, and production is down 9%. It would take 19.76 ÷ 4.5 = 4.4 trucks to keep the loader busy, so in the wet, a fifth truck would bring production back up to the loader's limit of 111 loads.
The numbers to get right
- Average speeds for each road condition, from your own experience or site records
- Time at the loader, which depends on the loader, the bucket and the material
- Payload, limited by the truck's legal and rated capacity as well as its tray
- Productive minutes per hour and hours per shift, after pre-starts, breaks and refuelling
The figures in this example are assumptions for the arithmetic. Use your own.
Seeing it
This is the calculation behind most haulage spreadsheets. If you have one, we can turn it into a 3D visual that runs on your numbers, so you can show a client how the haul works and what a wet day does to it. For the volume side, see how to calculate trench volume, then what each tonne costs to move.