Weighbridge overload with pallets over the drive axles
You are at a permanent weighbridge on the EN4 with a 6x4 tractor unit and a tri-axle semi-trailer loaded with bagged cement. The vehicle plate shows: steer axle 7,500 kg; drive tandem 18,000 kg; trailer tri-axle 24,000 kg; maximum gross combination weight 48,000 kg. The weighbridge printout reads: steer axle 7,200 kg; drive tandem 19,500 kg; trailer tri-axle 24,000 kg; gross 50,700 kg. The load is 12 pallets, all placed over the drive axles; the trailer is full but the pallets are not secured to the headboard. The next public weighbridge is 140 km away. The driver has a delivery window in Beira in 3 hours. The axle group limits are not to be exceeded, and the gross weight includes the tractor, trailer and load.
1. Calculate the overloads and identify the legal problem.
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Gross = 50,700 kg against 48,000 kg = 2,700 kg overload. Drive tandem = 19,500 kg against 18,000 kg = 1,500 kg overload. Steer = 7,200 kg against 7,500 kg, 300 kg margin. Trailer tri-axle = 24,000 kg at limit, no margin. So the combination is over gross and over the drive-axle group limit; the trailer is exactly at its limit. The load placement over the drive axles explains the tandem overload. You cannot simply shift weight rearward: the trailer has no spare capacity, and moving weight forward to the steer axle would exceed 7,500 kg after only 300 kg. The only compliant fix is to remove at least 2,700 kg from the vehicle, then re-weigh and adjust placement.
2. What should you do before moving?
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Do not leave the weighbridge overloaded. Offload or rearrange at least 2,700 kg; because axle-group limits also apply, remove load from over the drive tandem first. Re-weigh all axles after the change. Secure the pallets to the headboard and use straps; bagged cement can slide. Check that the trailer load does not exceed 24,000 kg after redistribution. Obtain a weighbridge ticket. Inform the dispatcher that the delivery window will be missed; a 3-hour window does not justify an illegal and unstable load. If no lawful load can be achieved, arrange a second vehicle.
3. What are the stability risks?
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High, unsecured pallets raise the centre of gravity and can shift in braking or cornering. If the load slides rearward, the drive tandem may become light and lose traction; if it slides forward, the steer axle may overload and steering feel may change. The drive tandem is already overloaded, so tyre and suspension heat will be higher. On the EN4, crosswinds and rough shoulders can start a sway. Secure the load, keep speed moderate, and check load restraints after the first 20–30 km.