Loading a flatbed for a bridge with a posted limit
A driver is loading a rigid flatbed truck with GVM 15,000 kg and tare 8,000 kg. The load is six steel coils, each weighing 1,100 kg, to be carried 40 km to a customer. The route crosses a bridge with a posted mass limit of 20 t. The truck's payload limit is therefore 7,000 kg by GVM, but the driver also needs to consider axle limits: the front axle is rated 6,000 kg and the rear axle 10,000 kg. The coils are currently stacked two-high at the rear of the tray, with the rear axle load estimated at 11,500 kg and the front axle at 5,500 kg. The driver wants to leave immediately to make the delivery window.
1. Is the vehicle legal to drive as loaded? Show the calculations.
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No - it is overloaded on the rear axle and the total is close to the bridge limit.
Calculations:
- Total load: 6 coils × 1,100 kg = 6,600 kg. This is under the 7,000 kg payload limit, so GVM is satisfied in principle (8,000 + 6,600 = 14,600 kg, under 15,000 kg).
- Rear axle: estimated 11,500 kg against a rated 10,000 kg - 1,500 kg over. Illegal.
- Front axle: 5,500 kg against 6,000 kg - legal.
- Bridge limit: total 14,600 kg is under 20 t, so the bridge posting is not breached.
The problem is load distribution, not total mass. The two-high stack at the rear puts too much weight on the rear axle. The driver must redistribute the load - for example, spreading the coils along the tray and moving some forward - then re-check axle loads before departing. Leaving immediately would be driving an overloaded vehicle.
2. What loading and restraint principles should the driver apply before leaving?
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The driver should apply these principles:
- Distribute weight correctly. Spread the coils along the tray so the load is shared between axles and neither exceeds its rating. Moving mass forward reduces the rear axle load and increases the front - re-check both after adjustment.
- Keep the centre of gravity low and central. Two-high stacking raises the centre of gravity and worsens rollover risk; a single layer spread out is safer where space allows.
- Restrain the load properly. Coils are round and can roll. They need chocks, cradles or dedicated coil racks, plus straps or chains rated for the load, with the restraint capable of withstanding the forces in braking and cornering - not just enough to stop the load sliding in a straight line.
- Check axle and total mass after loading, ideally at a weighbridge, and keep the documentation.
- Check the route for bridge limits and any other mass or height restrictions; the 20 t bridge is fine at 14,600 kg, but the driver should confirm no other restriction applies.
- Re-check the restraint after the first few kilometres, since loads settle.
Only after these checks should the vehicle depart.