# How to get optimum results out of the trucks calculation in MineSched

Defining haul truck speed for a haul road is an important step to calculate the number of trucks required to mine the required tonnes from each mining location.

One of the factors affecting truck speed is haul road gradient, and adding truck speed (for loaded and empty trips) based gradient manually is not an efficient way.

There are some tricks that may help you to set the truck speeds.

Step 1
In 2019, new Surpac version string files saved automatically as Binary, which will not be converted to csv file.

TIP: change the main Surpac setup to automatically save the string files as Text to eliminate any double work.

Go to:

Customise>Plugin preference>Surpac –  chose Text instead of Binary.

Step 2
Create your haul road using pit design and topography to the desired destination and save it.

Step 3
Open string math for all points in a layer and use the formulas below to populate the speeds in the description (D) fields.

To explain the formula:

– On d1 field, _prev_slope means calculate the slope between every two points on the string.

– On d2 field, iif(d1>8,12,20) means if the gradient set on d1 field greater than 8% (for example) use speed 12km/hr, else use 20km/hr.

– On d3 field, iif(d1>8,25,30) means if the gradient on the d1 field greater than 8% use speed of 25 else uses 30km per hour.

Remember there are inputs for empty and loaded average truck speeds and two-speed sets for ramps and for leveled haul roads. So you can use d2 for loaded haul road and d3 for empty haul roads.

Step 4
To overcome the underestimation of the number of trucks required, which can happen if inaccurate speeds are defined and which have been resolved on the previous point. We can now go through with feeding Minesched with speeds defined on d2 and d3 fields.

Step 5
Under Haulage, you can start by adding a new road string file.

On full velocity, you can choose the d field dedicated for full trucks and the same for empty.

On haulage route, you can see speed variation between the full path and empty path, which will give the user an accurate truck calculation.

Under Create schedule, you can create a custom report showing number of trucks required versus truck hours.

Please note that this workflow is for clients that do not use the Rim-pull Curve method of determining the truck requirements.

#### Ahmed Rezk

Ahmed holds a Mining Engineering degree and has more than 9 years of experience in open pit mining engineering including budgeting, regulating, planning, scheduling, design and management of production operations and waste disposal. He recently joined GEOVIA as an Industry Process Consultant. Former roles undertaken by Ahmed include Open Pit Engineering Superintendent for CIT and Open Pit Senior Mine Planning Engineer for Sukkari Gold Mine – Centamin.