Forty-foot container at the Douala port exit
At 06:10 a five-axle articulated combination leaves the Douala port area for Yaoundé. The tractor has three axles (steering plus tandem drive) and the skeletal trailer has a tandem. The driver holds a weighbridge ticket from inside the port: steering axle 7.2 t, drive tandem 22.6 t, trailer tandem 14.0 t, gross 43.8 t. The 40-ft container holds steel coils loaded at the front; container and chassis tare are already included in the figures. The company's operating limit is 44 t gross and 21 t for any tandem group; the steering axle limit is 8 t. The trailer bogie is currently in its forward position. The driver plans to take on 300 litres of diesel (about 0.25 t) at the next station and to carry two passengers in the cab. The dispatcher says the port ticket is 'only a formality' and that the N3 weighbridge at Boumnyebel is not always operating.
1. Using only the ticket figures and the limits given, may the combination leave the port? Show your arithmetic and identify the binding constraint.
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No. The arithmetic is straightforward:
- Gross: 7.2 + 22.6 + 14.0 = 43.8 t, against a 44 t limit - only 0.2 t of headroom.
- Steering axle: 7.2 t against 8 t - 0.8 t of headroom.
- Trailer tandem: 14.0 t against 21 t - 7.0 t of headroom.
- Drive tandem: 22.6 t against 21 t - 1.6 t over the limit.
The binding constraint is therefore the drive tandem, not the gross weight. The margin on gross is illusory because the planned fuel and passengers are not yet on the ticket: 0.25 t of diesel plus roughly 0.15 t of people takes the gross to about 44.2 t, which breaches the 44 t limit as well. Fuel sits mainly on the tractor and passengers on the steering axle, so both the gross and the steering-axle figures move in the wrong direction. The driver may not leave the port as loaded; the load must be redistributed and the combination re-weighed before departure.
2. What is the most effective adjustment available with the equipment on hand, and why is sliding the tractor's fifth wheel forward not the best answer? State what must be re-weighed.
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The best available adjustment is to slide the trailer bogie rearward. Moving the trailer axle group further behind the container lengthens the distance from the kingpin to the trailer suspension, so the trailer tandem carries a larger share of the container weight and the kingpin transfers less load onto the tractor's drive tandem. The trailer tandem has 7 t of unused capacity, while the drive tandem is 1.6 t over, so this is the correct direction of transfer.
Sliding the fifth wheel forward would move load from the drive tandem onto the steering axle, but that axle has only 0.8 t of headroom - less once two passengers are aboard - and the gross weight would be unchanged at about 44.2 t after refuelling. It would also alter the tractor's handling and could overload the steer tyres. It treats the symptom on one axle while creating a second breach.
After moving the bogie, the driver must re-weigh all three axle groups and the gross, with fuel and occupants representative of departure. Confirm: drive tandem ≤21 t, steering ≤8 t, trailer tandem ≤21 t, gross ≤44 t. Then check that the bogie locking pins are fully engaged, tyre loads are within tyre ratings, and the twist locks and container seal are still secure.
3. Which documents and load-security checks must be in order before the truck leaves the port, and what should the driver do about the dispatcher's instruction?
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The driver should check the vehicle's carte grise, valid visite technique, third-party insurance, the transport title or carte de transport, the lettre de voiture matching the container number and seal, the weighbridge ticket, and a driving licence of the correct category with the professional card where required. The container number on the waybill must match the box, the seal must be intact and recorded, and the twist locks must be visibly engaged.
For load security, the steel coils are the critical item: they must be blocked or choked so they cannot shift forward under braking, and any internal securing points must be checked. If the container is already sealed and the coils cannot be inspected, the driver should record that limitation and confirm with the shipper that the stow is rated for road transport.
On the dispatcher's instruction, the driver should not treat the ticket as a formality. The driver is the person who signs the inspection and takes the vehicle onto the road. The correct response is to state in writing that the drive tandem is 1.6 t over the company limit and that the gross will exceed 44 t after fuel and passengers, request the bogie adjustment and re-weigh, and refuse to depart until the ticket is clean. An overloaded axle is not a paperwork problem: it damages the pavement, overheats tyres, lengthens stopping distance and can void insurance cover after a crash.