Winter Pre-Trip Check: Air Brakes, Tyre and Steering Defects
It is 05:40 in January, −3 °C, at a depot near Ioannina. Dimitris is due to take a 12-metre coach on a school run. During the walk-around he finds: the air-pressure gauge has reached only 5.5 bar after four minutes of idling and the low-pressure warning buzzer is still on; there is a faint hiss from the rear axle area; the steering wheel has about 40 mm of free play; the front right tyre has a 3 cm cut exposing the white cords; and the ABS warning lamp stays on after the self-test. The brake pedal feels firm. The depot has no spare tyre, and the school is 25 km away on a mountain road. The previous driver wrote 'brakes OK' in the defect book. Dimitris is under pressure because the school has an exam at 08:00.
1. Explain what each of the five findings indicates and rank them by seriousness for a coach carrying passengers.
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Air pressure: a healthy system should build to its cut-out pressure, typically around 8–10 bar, within a short time and then hold it. 5.5 bar after four minutes, with the low-pressure warning still on, means the system is not charging properly; with insufficient pressure the spring brakes may not fully release and the reserve for repeated braking is inadequate. The hiss points to an air leak, likely at a diaphragm, valve or pipe union near the rear axle.
Steering free play of about 40 mm is excessive for a coach and points to wear in the steering linkage or box. The tyre cut exposing cords is a structural failure: the tyre can burst, especially under load and heat. The ABS lamp means the anti-lock function is faulty; the basic brakes may still work, but wheel-lock protection is lost.
Ranking: 1 tyre cut (immediate risk of blow-out), 2 air-pressure leak (risk of brake loss or spring brakes not releasing), 3 steering free play (loss of steering control), 4 ABS fault. The tyre and the air system alone make the vehicle unroadworthy; the order among them depends on which would fail first, but both are prohibition-level defects.
2. May Dimitris take the coach? Set out what must happen before the school run can proceed.
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No. A vehicle with a tyre exposing cords, a leaking air-brake system and excessive steering play must not carry passengers. The previous driver's 'brakes OK' entry is irrelevant; the driver must make his own assessment.
He should switch off, secure the vehicle and report the defects. The operator must be told immediately so that a replacement coach can be sent or the trip cancelled. A mechanic should trace the air leak, test pressure build-up and leak-down, replace the tyre and investigate the cause of the cut, check the steering and diagnose the ABS. The school should be informed of the delay.
The coach must not be driven even the 25 km to the school, and certainly not with children on board. A defect of this kind is a prohibition-type defect. If a replacement vehicle cannot be provided, the run does not go ahead. The pressure of the 08:00 exam does not change the legal duty: the driver is responsible for the safety of the passengers and for the roadworthiness of the vehicle.
3. What should he write in the defect book and what should he report to the operator?
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In the defect book he should enter the date, time, registration, mileage and each defect with measurements: 'air pressure only 5.5 bar after 4 min, low-pressure buzzer on, hiss at rear axle'; 'steering free play approx. 40 mm'; 'front right tyre cut 3 cm, cords exposed'; 'ABS lamp on'. He should mark the vehicle 'VOR - not to be used' and sign it.
He should tell the operator or transport manager directly, not just leave the book, and ask for a replacement vehicle and a fitter. He should not sign a nil-defect declaration, and should not rely on the previous driver's entry. He should also make sure the vehicle cannot be taken out by someone else: control the keys and put a defect tag on the steering wheel. If the operator pressures him to take it, he should refuse and record that refusal.