Load Planning for Side-Tippers: Payload and Turnaround

Published: 14 August 2026
Updated: 30 October 2026

Load planning for side-tippers in South Africa is a daily balancing act. Load too light and you leave revenue on the ground; load too heavy and you risk overloading charges, delays at the weighbridge, extra wear on the vehicle and damage to your compliance record. Good load planning sets a target mass for every vehicle configuration, weighs every load at source, distributes it correctly across the axles and records the result. Done well, it also shortens turnaround, because trucks that leave correctly loaded do not get stopped, offloaded or sent back.

This guide covers the legal mass limits that shape side-tipper loading, the bridge formula, how moisture and material density affect payload, weighbridge practice, which commodities suit side-tipping, how to measure cost per tonne-kilometre, and how to manage turnaround time across dispatch, loading queues, POD and tracking. For a complete reference on staying within mass limits, see our pillar overloading management guide.

Why Load Planning Matters for Bulk Haulage

Side-tippers moving coal, chrome, manganese, aggregate, sand and agricultural commodities are usually paid per tonne. That makes payload accuracy a direct revenue question:

• Under-loading costs revenue. If a truck routinely runs a tonne or two below its legal payload "to be safe", every trip earns less than it could. Over hundreds of trips a month, that adds up quickly.
• Overloading costs money and time. An overloaded vehicle can be fined, held at a weighbridge until the excess is removed, and recorded against the operator. Fines can be significant and repeated offences attract closer attention from enforcement and from customers. Our guide to the overloading fines schedule covers the penalties in detail.
• Overloading wears out vehicles. Persistent overloading accelerates tyre, suspension, brake and chassis wear, and damages roads.
• Customers and schemes check it. Mines, ports and large consignees increasingly expect transport contractors to show documented load management, and the RTMS self-regulation scheme treats load management as a core requirement.

What Are the Legal Mass Limits for Side-Tippers?

South African mass limits are set in the National Road Traffic Regulations. The permissible mass of a vehicle or combination is the lowest of several limits, so you need to check all of them, not just the total:

1. Manufacturer's ratings - the gross vehicle mass (GVM), gross combination mass (GCM), and axle and axle unit ratings on the vehicle's information plate. These may not be exceeded.
2. Axle and axle unit limits - legal maximum loads per axle and axle group.
3. The bridge formula - a limit on the total load of any group of axles based on the distance between them.
4. The regulated maximum combination mass for the vehicle combination. Regulation 237 caps any combination at 56,000 kg, however many axles it has.
5. Tyre load ratings, and the minimum share of mass on the drive axles.

Axle and axle unit limits

The Department of Transport's TRH 11 guideline (8th edition, 2010) sets out the legal axle loads under Regulation 240 of the National Road Traffic Regulations as follows:

| Axle type | Single axle | Two-axle unit | Three-axle unit |
|---|---|---|---|
| Steering axles | 7,700 kg | 15,400 kg | 23,100 kg |
| Non-steering axles (single wheels) | 8,000 kg | 16,000 kg | 24,000 kg |
| Axles with dual wheels | 9,000 kg | 18,000 kg | 24,000 kg |

The same document notes that the mass carried on the drive axles must not be less than 20 per cent of the total mass of the vehicle or combination. Regulations are amended from time to time, so confirm current figures against the latest National Road Traffic Regulations or with the RTMC before building them into your loading rules.

The bridge formula

Regulation 241 limits the total mass on any group of axles to protect bridges and culverts. As set out in TRH 11, the permissible maximum mass of a group of axles is:

P = 18,000 + 2,100 x L

where P is the maximum mass of the axle group in kilograms and L is the distance in metres from the centre of the first axle to the centre of the last axle in the group, rounded up to the next tenth of a metre.

Worked example: a tridem trailer axle group measuring 2.8 m from first to last axle gives P = 18,000 + (2,100 x 2.8) = 23,880 kg. That is lower than the 24,000 kg axle unit limit for dual-wheel tridems, so for this axle group the bridge formula is the limit that applies. This is why a vehicle can be within its GCM and still be overloaded: the load is concentrated over axles that are too close together.

How Moisture and Density Affect Payload

Bulk materials are not consistent. The same bucket count can produce quite different masses depending on:

• Moisture - coal, sand and fine ores take on water after rain or from stockpile watering, which adds mass without adding saleable product.
• Particle size - fines usually hold more moisture and pack more densely than lump material.
• Source - material from different pits, benches or stockpiles can differ in density.
• Season - summer rainfall regions see bigger swings in moisture than dry months.

Practical ways to manage this:

• Get information from the source. Many mines and quarries test moisture as part of quality control. Ask for the readings.
• Adjust targets, not guesses. Agree loading guidelines with each loading point, for example reducing the bucket count when material is visibly wet or moisture readings are high.
• Weigh before leaving site. An on-site weighbridge is the last chance to correct a load cheaply.
• Build a history. Recording mass, material, source and conditions for every load shows which loading points and materials need wider margins.

Weighbridge Strategy for Side-Tipper Operators

• Weigh every load at source wherever a weighbridge is available, and require a weighbridge ticket before the truck leaves.
• Set a target band, not just a maximum. Loading to a target slightly below the legal limit allows for differences between weighbridges and for load settling, while keeping trucks close to full payload.
• Use axle-by-axle readings. A total mass reading will not show a distribution problem. Where possible, use weighbridges that report axle unit masses.
• Keep calibration records for any private weighbridge you operate.
• Keep your own records. If you believe a reading is wrong, your source weighbridge tickets and history support a re-weigh request or a dispute.
• Know your routes. Note which routes pass public weighbridges and set targets accordingly.

Distributing the Load Correctly

Getting total mass right is only half the job. How the load sits across the axles determines whether each axle unit and axle group is within its limit.

• Loader technique - concentrating material at the front of the bin loads the truck-tractor's drive axles; concentrating it at the rear loads the trailer axles. Brief loader operators on where to place material for each configuration.
• Settling - bulk material settles and can shift in transit, so a load that is borderline at the mine may be over on one axle unit at a roadside weighbridge.
• Bin design - sloped floors and bin shapes affect how material spreads. Consider this when specifying new trailers.
• Check axle units, not just totals - this is the only way to catch distribution problems before enforcement does.

Commodity Suitability and Cost per Tonne-Kilometre

Most side-tippers on South African public roads run as interlinks: a truck-tractor pulling two side-tipping trailers. The configuration question is therefore rarely "interlink or side-tipper". It is whether side-tipping suits the material and the discharge point, and what each tonne actually costs to move.

Which materials suit side-tipping

Side-tipping works best with free-flowing bulk material that is discharged alongside the vehicle: coal, chrome, manganese and other ores, aggregate and sand tipped into rail siding pits, tipping grids or onto stockpiles. Before committing side-tippers to a contract, check:

• The discharge point. Side-tippers need firm, level ground and clear space on the tipping side. A receiving site built around end-tipping or a narrow grid may not suit them.
• Material behaviour. Wet, sticky or cohesive material (some clays, very wet fines) can hang up in the bin instead of discharging cleanly. If a material regularly needs manual clearing, the turnaround advantage disappears.
• Mass-limited or volume-limited. Dense ores reach the legal mass with the bins only partly full, so payload is set by the mass limits and load distribution matters more than bin size. Lower-density material, such as some coals, can fill the bins before the truck reaches its legal mass, so bin volume sets the payload. Know which case applies to each commodity before you quote a per-tonne rate.

Payload starts with tare

Legal payload is the permissible mass, the lowest of all the limits above, minus the tare of that specific combination. Tare differs between combinations of different specification, so two interlinks in the same fleet can have different payloads. Weigh each combination empty, record the tare and work out its payload target from that, not from a fleet average.

How to calculate cost per tonne-kilometre

Per-tonne work should be costed per tonne-kilometre, because it puts different vehicles, routes and contracts on the same basis:

Cost per tonne-km = total round-trip cost / (payload in tonnes x loaded kilometres)

Total round-trip cost includes the empty return leg, fuel, tolls, tyres, maintenance, driver costs and a share of fixed costs and overheads. Three things follow from the formula:

• Payload shortfall raises cost directly. If the trip costs the same either way, carrying 32 tonnes instead of 34 tonnes raises the cost per tonne-km by about 6%. Chronic under-loading is a cost problem as well as a revenue problem.
• Empty running is carried by the loaded leg. Most mineral haulage returns empty, so the loaded tonnes must pay for both legs.
• Waiting time is a cost. Hours queuing at loading and offloading points still carry fixed costs and driver pay, spread over the same tonnes.

Compare your cost per tonne-km with the rate per tonne divided by the loaded distance. If the rate does not cover the cost, more trips will not fix it. Our guide to freight rate benchmarks shows how to build the full trip cost, and fleet cost per kilometre covers the underlying cost data.

Managing Turnaround Time in Bulk Haulage

For per-tonne work, turnaround is the other half of profitability. A truck earns when it is moving loaded; every hour queuing at a loading point, waiting for paperwork or standing at a congested offloading site is lost capacity.

Illustrative example: if a side-tipper on a fixed route currently completes three round trips every two days (1.5 per day) and better turnaround lets it complete two a day, it carries a third more loads with the same truck and driver. Your own figure will depend on route length and where the delays sit.

Where turnaround time is lost

| Stage | Typical causes of delay | What helps |
|---|---|---|
| Dispatch | Trucks waiting for allocation, unclear instructions | Trips allocated in the system with the right truck matched to the load |
| Queue at loading point | Arrivals bunched together, no slot booking | Spreading arrivals, sharing ETAs with the loading point |
| Loading and weighing | Re-loading after overweight or underweight readings | Target masses per configuration, briefed loader operators |
| Transit | Poor road conditions, overload stops | Correct loading, route planning |
| Offloading | Queues at the receiving site, missing paperwork | Accurate ETAs, documents ready digitally |
| POD and paperwork | Paper notes returned days later | Digital POD captured at delivery |
| Return leg | Waiting for the next allocation | Next trip allocated before the truck is empty |

Dispatch

Allocation that relies on one experienced dispatcher works until that person is away. When trips are allocated in the system, matching vehicle configuration, driver availability and hours, and load requirements, trucks spend less time waiting and every allocation is recorded. Dispatchers still handle exceptions and customer escalations; the system takes the routine work.

Queue time at loading and offloading points

Measure the time from arrival to departure at each site. Once you have the data, you can agree arrival windows with mines and plants, spread your fleet's arrivals, and raise waiting time with customers using evidence rather than anecdotes.

Weighbridge data linked to the trip

When gross, tare and net mass from the source weighbridge are recorded against the trip, the same figure serves compliance (the load was legal), operations (payload against target) and billing (the tonnage invoiced). In T-ERP the driver photographs the ticket and the masses are read into the trip, which is how weighbridge tickets feed trip-based invoicing. That removes manual capture and the quantity disputes it causes.

POD and tracking

Paper PODs that come back with the driver days later delay invoicing and leave turnaround data incomplete. A digital POD records the delivery time, location and quantity on the spot; our guide to digital proof of delivery explains what to capture. Combined with tracking, it gives a full timeline for every load: loaded, weighed, departed, arrived, offloaded, delivered.

Building a Load Management System

Step 1: Record vehicle specifications. For each vehicle and combination, record the manufacturer's ratings, axle unit limits, bridge formula results and target loading mass.

Step 2: Agree loading procedures with each loading point. Decide who makes the final call on mass, what happens when a load is over or under target, and how moisture or material changes are communicated.

Step 3: Set weighing rules. Every load is weighed before leaving the loading point, the weighbridge ticket travels with the trip, and discrepancies are resolved before dispatch.

Step 4: Track every load. Log mass against vehicle, driver, material, source and route, and flag loads outside the target band.

Step 5: Review monthly. Look for chronic under-loading (lost revenue), over-loading (compliance risk), loading points that need better coordination and drivers or loader operators who need training.

Step 6: Document corrective action. When an overload happens, record the cause and what was done to prevent a repeat. RTMS audits look for this evidence of continuous improvement.

Using Technology to Support Load Planning

• On-board weighing - load cells or suspension pressure sensors give the driver and loader operator a mass reading during loading.
• Weighbridge integration - digital weighbridge tickets captured against the trip instead of retyped.
• Telematics - location, timing and vehicle data that feed turnaround measurement.
• Trip and load records - mass, material and source history that shows patterns by loading point, material and driver.
• Compliance reporting - load records and corrective actions ready for RTMS and customer audits.

T-ERP's transport management software for haulage operators records trips with weighbridge masses, flags loads outside the target band for each vehicle configuration, captures digital POD and keeps the history needed for audits and turnaround reporting.

How Mining Operations Differ

• Mine roads versus public roads - vehicles on private mine haul roads operate under the mine's rules, but every vehicle must be legally loaded before it enters a public road.
• Weighbridge bottlenecks - high-volume mines can have long queues at the weighbridge. Scheduling arrivals and sharing ETAs helps.
• Material variability - different pits or levels may need different load targets.
• Safety systems - load management must fit with the mine's broader traffic and safety requirements.
• 24-hour operations - loading rules must hold on night shift as well as day shift.

Conclusion

Effective load planning for side-tippers comes down to knowing your limits, loading to a target and proving it. Check every limit that applies, from manufacturer's ratings and axle units to the bridge formula, set target masses for each configuration, manage moisture and density at source, weigh every load before it leaves and make sure the mass is distributed correctly. Then treat turnaround as part of the same system: allocate trips promptly, measure queue time, link weighbridge data and digital POD to each trip, and review the results every month.

Measure the result in cost per tonne-kilometre, so payload, empty running and waiting time all show up in one number. Operators who run load planning as a system, rather than leaving it to individual judgement at each loading point, carry more tonnes legally with the same fleet. When you are ready to set this up for your operation, schedule a consultation.

Sources

• Department of Transport - TRH 11: Dimensional and Mass Limitations and Other Requirements for Abnormal Load Vehicles (8th edition, 2010) - legal axle loads under Regulation 240, bridge formula under Regulation 241, manufacturer's ratings and the 20 per cent drive axle requirement
• National Road Traffic Regulations, 2000 - regulation 237, permissible maximum combination mass (Acts Online) - 56,000 kg cap on combination mass; regulations 234 to 241 on loads on vehicles
• Road Traffic Management Corporation (RTMC) - road traffic regulation and enforcement
• Road Transport Management System (RTMS) - industry self-regulation scheme covering load management

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The information in this article is for general guidance only. Regulations and requirements may change - always verify current requirements with the relevant South African regulatory authority.

Frequently Asked Questions

What is the maximum legal mass for a side-tipper in South Africa?

There is no single figure. The legal mass is the lowest of the vehicle's manufacturer's ratings, the axle and axle unit limits, the bridge formula result for each axle group and the regulated maximum combination mass. For example, TRH 11 lists 18,000 kg for a two-axle unit with dual wheels. Check every limit for each configuration in your fleet against the current regulations.

What is the bridge formula?

The bridge formula limits the total mass on any group of axles according to the distance between the first and last axle in the group. As set out in TRH 11, it is P = 18,000 + 2,100 x L, with P in kilograms and L in metres rounded up to the next tenth. A closely spaced axle group can therefore carry less than its axle unit limit.

How does moisture affect side-tipper load planning?

Wet material weighs more for the same volume, so a bucket count that is legal in dry weather can overload a truck after rain. Fines and some ores hold more water than lump material. Ask loading points for moisture readings, adjust loading guidelines when material is wet, weigh every load before it leaves site and record conditions so you can refine targets over time.

How can bulk haulage operators reduce turnaround time?

Measure each stage of the trip first: allocation, queueing, loading and weighing, transit, offloading and POD. Then fix the biggest delays, for example by allocating trips in the system, agreeing arrival windows with loading points, loading to set targets so trucks are not re-weighed or offloaded, and capturing digital POD at delivery so paperwork does not hold up invoicing.

What load management records does RTMS expect?

RTMS expects operators to show that load management is systematic: documented procedures, records of load masses, evidence that drivers and loader operators are trained, regular internal checks and documented corrective action when an overload occurs. Keeping weighbridge tickets, load history and corrective actions in one system makes it much easier to produce this evidence at an audit.

How do I calculate cost per tonne-kilometre for side-tipper work?

Divide the total round-trip cost, including the empty return, fuel, tolls, tyres, maintenance, driver costs and a share of fixed costs and overheads, by the payload in tonnes multiplied by the loaded kilometres. Use each combination's actual tare to set its payload, and compare the result with your rate per tonne divided by the loaded distance.

Which materials suit side-tippers best?

Free-flowing bulk material that can be discharged alongside the vehicle, such as coal, ores, aggregate and sand tipped into siding pits, grids or stockpiles. Side-tippers need firm, level ground on the tipping side, and wet or sticky material can hang up in the bin.