Loaded Lorry Pre-Trip: Brake Buzzer and Exposed Cord
At 06:10, a driver is about to leave a maize mill yard in Bungoma with a three-axle rigid lorry rated at 28 tonnes gross vehicle weight. The lorry carries 18 tonnes of bagged maize. During the walk-around, the driver notices that the air-brake low-pressure warning buzzer sounds continuously when the engine is idling and does not stop after five minutes. The left inner rear tyre has exposed cords over a 60 mm patch, and the load is stacked 0.5 m higher on the right side. The tarpaulin is torn and two rear marker lamps are cracked. The driver is already 40 minutes late for a 300 km delivery to Eldoret, and the fleet controller tells him to 'sort it at the weighbridge.' The yard has no workshop, but a tyre bay is 300 m away and a mechanic is on call. It is raining lightly.
1. Decide whether the lorry is roadworthy and rank the defects in order of risk.
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The lorry is not roadworthy. The air-brake low-pressure warning that sounds continuously and does not stop after five minutes is the highest-risk defect: it indicates the system is not building or holding adequate pressure, so service braking and parking braking may be unreliable. The exposed cords on the left inner rear tyre are the second critical defect; that tyre can fail under load and heat, and on a three-axle lorry a rear tyre failure can cause loss of control or load shift. The uneven load stacked 0.5 m higher on the right is third: it raises the centre of gravity and shifts weight to the right-side tyres and suspension. Cracked marker lamps and a torn tarpaulin are lower-risk but still defects because lighting and load protection are required.
'Sorting it at the weighbridge' is not acceptable; a weighbridge checks mass, not brake pressure or tyre condition. The driver should not move the loaded lorry except under controlled repair movement.
2. Explain how the brake fault, tyre defect, and load distribution affect stopping distance and stability on the wet road.
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Low air pressure reduces the force available at the brake chambers, so pedal travel increases and braking may be uneven or delayed. On a wet road, available friction is already lower, so any lag in brake application lengthens stopping distance. The exposed-cord tyre has reduced structural strength and heat resistance; under a 28-tonne gross vehicle weight it can burst, and if it is an inner rear tyre the failure may not be immediately visible to the driver.
The right-side load bias means the right tyres carry more vertical load and the left inner tyre may be partially unloaded, which worsens traction and can promote a pull to the right under braking. A high centre of gravity increases roll moment in a curve or sudden steer. The safe response is to reduce speed before moving at all, repair the brake system and tyre, redistribute the load, and check tyre pressures and lamp function.
3. List the actions and records required before the lorry leaves the yard.
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Actions: notify the fleet controller in writing that the vehicle is unroadworthy; call the mechanic to diagnose the air system; replace or repair the exposed-cord tyre; redistribute and secure the maize; repair or replace the torn tarpaulin and cracked lamps; clean the number plate and lights; check tyre pressures and wheel nut indicators; conduct a brake test after repair.
Records: a pre-trip inspection sheet showing each defect, the time, the driver's name, and the action taken; a maintenance job card; the mechanic's release note; and a revised dispatch time. If the controller insists on departure, the driver should refuse in writing and escalate to the operator's safety officer. The driver should not sign a clean inspection sheet.