Cold-morning pre-trip check with ABS and pressure warnings
At 05:40 in January, the driver of a 24-seat category D minibus starts a pre-trip check. Temperature is -3 °C; the bus was parked outside overnight. The air-pressure warning lamp stays on after 3 minutes of idling, and the ABS lamp remains lit after the self-test. The front tires look slightly soft; the driver's gauge reads 4.2 bar on the left front and 5.0 bar on the right front; the manufacturer specifies 5.5 bar for both. The washer fluid is frozen, and the passenger door closes slowly. The first run is a school contract at 06:30, 18 km with a mountain pass. The driver has a spare can of washer fluid but no compressor. The operator's workshop opens at 08:00. The driver's licence and CPC card are valid. The tachograph shows a previous fault code that was cleared yesterday.
1. Which defects are 'do not depart' and which can be managed? Justify each.
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The air-pressure warning lamp staying on after 3 minutes is a 'do not depart' defect. The brake system may not be building enough pressure, and a bus with uncertain braking cannot carry passengers, especially on a mountain pass. The ABS lamp also indicates a fault; ABS may not operate, and on a cold pass that increases skid risk. The tyre readings are both below the specified 5.5 bar and differ by 0.8 bar; that is a 'do not depart' defect until corrected, because low or mismatched front tyre pressures affect steering and braking and increase blowout risk. The frozen washer fluid can be managed with the spare can, but only if visibility is clear; it is not a reason to cancel by itself. The slow-closing passenger door must be checked: if it latches securely and the warning lamp goes out, it can be monitored; if not, it is a do-not-depart defect. The cleared tachograph fault must be verified; if the fault returns, manual records are needed. Overall, the bus should not leave with the pressure, ABS and tyre defects.
2. What is the correct sequence for a brake test and pressure build-up, and what should the driver do if pressure does not rise?
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Correct sequence: chock the wheels, ensure the parking brake is applied, start the engine and let the compressor build pressure at idle. Watch the gauge and the warning lamp; the lamp should go out within the manufacturer's specified time. Do not drive to 'build pressure'. Once pressure is in range, switch off the engine and listen for leaks; a significant drop indicates a leak. Then perform a stationary brake test: apply the service brake and hold; check the pedal feel and that the bus does not creep. Test the parking brake on a slope if safe. If pressure does not rise, stop the check, do not move the bus, and report a brake-system defect. Do not try to adjust the compressor or bypass the warning. The driver should record the gauge readings and the time. If the workshop opens at 08:00, the bus waits or is swapped; the school run cannot use it.
3. How should the driver handle the 06:30 school contract?
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The driver must tell the operator immediately that the bus is unserviceable and that the 06:30 school contract is at risk. The operator should send a replacement bus or a qualified driver with a serviceable vehicle. The school should be informed of the delay or cancellation so children are not left unsupervised at the stop. The driver must not take the defective bus 'just this once' because the route is only 18 km; a mountain pass in freezing conditions is exactly where brake and tyre defects become dangerous. If no replacement is available, the contract should be cancelled rather than operated unsafely. The defect should be entered in the daily defect log, and the bus should not return to service until the pressure, ABS and tyre issues are rectified and signed off. The driver should also check whether the frozen washer fluid and slow door are recorded for the workshop.