You're stationary. The brake air-pressure warning light comes on. Why should you keep the parking brake on?
- A Because the vehicle will suddenly roll backwards
- B Because it will cause the air pressure to rise
- C Because the service brake may not stop you
- D Because it will make the warning light go out
Why this is the answer
Even though a warning device indicates low air-brake pressure, you may still be able to release the parking brake. If you do this and start moving, the service brake may be ineffective and you may not be able to stop.
Why the other answers don't fit
- A
- Because the vehicle will suddenly roll backwards — The vehicle rolls backwards only if there is a slope, and the light says nothing about that.
- B
- Because it will cause the air pressure to rise — Holding the parking brake does not make the compressor work any harder.
- D
- Because it will make the warning light go out — The light goes out when the pressure comes back, not because of which brake you use.
Where this comes from
- Driving Buses and Coaches — section 3, section 11
- Driving Goods Vehicles — section 3, section 11
Rule numbers link to The Highway Code on gov.uk.
Where this question comes from
The question, its options and the explanation are reproduced word for word from the DVSA revision question bank under licence. The licence requires them to appear unaltered, so we cannot reword them and neither can anyone else — that is why you will meet the same wording on other sites. Everything else on this page is written by Theory Hub: the explanation of why each wrong answer is wrong, the topic guide and the revision notes.
Asked in: Lorry & Bus (LGV/PCV)
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