Brake systems, compressed air, endurance brake/retarder, speed limiter
Design and function of the compressed-air brake with dual-circuit system, spring brake and trailer control, plus ABS/EBS, endurance brakes and driving downhill. Also the rules on braking performance, securing the vehicle and the speed-limiting device.
- 52 questions in this topic
- Topic 9 of 16 in the course: Bus & Coach – supplementary theory cat. D and D1
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From the key facts
- Brake systems must be able to bring the vehicle to a stop at all speeds and loads; depending on the class, service, secondary, parking and endurance brake as well as anti-lock system (VTS Art. 65).
- Parking brake: loaded truck on an 18 % downhill/uphill gradient, combination with trailer on 12 %; response and build-up time no more than 0.6 s (VTS Annex 7 no. 151, 213).
All key facts, the questions with explanations and the exam simulation are part of the course.
Sample questions from this topic
3 of 52 questions free to try. All questions with explanations and the exam simulation are part of the course.
Question 1: What basic requirement does the VTS impose on the brake systems of motor vehicles and trailers?
- They only have to act on the wheels of the drive axle.
- They only have to be able to stop the unladen vehicle safely from 50 km/h.
- They must be able to stop the vehicle at all speeds and loads.
Show answer
Correct answer: They must be able to stop the vehicle at all speeds and loads.
The VTS requires the brake systems to be able to stop the vehicle at all speeds and loads that occur – including when fully loaded and at maximum speed. There is no restriction to the empty vehicle or the drive axle.
Legal reference: VTS Art. 65 para. 1
Question 2: During the pre-departure check, how does Sven check in a simple way whether the compressed-air system is leak-tight?
- Open all drain valves with the engine running and let the pressure out
- At full pressure, switch off the engine, listen for hissing and watch the pressure gauge
- Spray the brake linings with soapy water and watch for bubbles
Show answer
Correct answer: At full pressure, switch off the engine, listen for hissing and watch the pressure gauge
When the system is full and the engine is off, the compressor supplies no more air; a clear drop on the pressure gauge or hissing indicates a leak. Emptying all reservoirs does not test leak-tightness, and there is no compressed air at the linings.
Legal reference: Practice (generally recognised); VZV Annex 12 no. III.E.1.2
Question 3: What is the function of the secondary brake?
- It brings the vehicle to a stop if the service brake fails.
- It holds the speed on long downhill gradients without wear.
- It reliably holds the parked vehicle stationary.
Show answer
Correct answer: It brings the vehicle to a stop if the service brake fails.
The secondary brake replaces the service brake if it fails and must be gradable. If each circuit of a dual-circuit brake meets this requirement, no separate secondary brake is needed. Holding the vehicle stationary is the job of the parking brake, wear-free deceleration on downhill gradients that of the endurance brake.
Legal reference: VTS Art. 65 para. 2; VTS Art. 128 para. 2
Legal references for this topic
The questions in this topic are based on these provisions:
- VTS Art. 21, 48, 65, 75, 90, 99, 99a, 103, 114, 127, 128, 130, 189; Annex 7
- VRV Art. 22, 23, 57, 70
- VZV Annex 11, Annex 12
- SVG Art. 45