65 LGV and PCV theory test questions on braking systems. Preview the questions below, or open one to read its answer and continue through the whole topic.
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When is trailer swing most likely to occur on a lorry and drawbar combination?
Question 1
1While you're braking on a bend
2While you're using an endurance brake
3While you're steering at slow speed and fully loaded
4While you're moving off at an angle
Show the answer
While you're braking on a bendRightThis was the right answer
The forces that act on your vehicle if you brake while cornering can lead to instability and may cause trailer swing. You should try to plan ahead so that you brake smoothly and in good time as you approach a bend.
Your vehicle is fitted with a 'diff-lock'. When would you normally use it?
Question 2
1While driving on straight roads
2While towing an empty trailer
3While driving on muddy construction sites
4While uncoupling a trailer
Show the answer
While driving on muddy construction sitesRightThis was the right answer
The differential allows the drive wheels to rotate at different speeds; this is necessary for the vehicle to negotiate corners and bends. On a slippery surface, however, it can cause problems: if one wheel has less traction, it can spin, resulting in a complete loss of drive. The 'diff-lock' prevents the wheels from turning independently and so helps to stop this happening.
On a legacy three-line trailer air-brake system, what colour identifies the auxiliary line?
Question 3
1Red
2Blue
3Green
4Yellow
Show the answer
BlueRightThis was the right answer
Blue identifies the auxiliary connection on this legacy arrangement. Follow the actual coupling instructions; do not apply the three-line diagram indiscriminately to a modern two-line system.
Your lorry has manually drained air reservoirs without an air dryer. What routine helps prevent accumulated moisture freezing in frosty weather?
Question 6
1Drain the air tanks daily
2Cover the air tanks with a blanket
3Keep the engine at high revs when starting
4Pump the brakes
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Drain the air tanks dailyRightThis was the right answer
For this system, drain the reservoirs daily using the manufacturer’s safe procedure. Vehicles with air dryers or automatic drains have different maintenance schedules; check the handbook rather than assuming daily manual draining suits every vehicle.
1Ensure that the air tanks are drained before journeys
2Check that the air pressure is correct
3Make sure that the parking brake is applied before stopping
4Select an appropriate gear before downhill gradients
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Select an appropriate gear before downhill gradientsRightThis was the right answer
Using the brakes to control a lorry's speed as it's driven down a hill will cause them to get hot. If they overheat, they can become less effective - a condition known as brake fade. By selecting a low gear, the engine's resistance will slow the lorry. This reduces the demands on the brakes, making them less likely to overheat.
For an exhaust brake whose handbook specifies a higher-rpm braking range, which driving combination makes effective use of it?
Question 8
1A suitable lower gear that keeps engine speed in its permitted braking range
2At low engine speed, while in high gears
3During stop/start town work
4While travelling at a constant speed on a motorway
Show the answer
A suitable lower gear that keeps engine speed in its permitted braking rangeRightThis was the right answer
Use an appropriate gear to stay within the manufacturer’s engine-braking range. DAF’s LF guide describes using its blue band. Never enter the red range or over-rev; the actual engine and road conditions govern.
What's the principal braking system on a lorry called?
Question 9
1The endurance brake
2The service brake
3The parking brake
4The jake brake
Show the answer
The service brakeRightThis was the right answer
The service brake is usually operated by the brake pedal. It's used to control the speed of the vehicle and to bring it to a halt safely. It may also incorporate an anti-lock braking system.
You're driving an articulated lorry. What could happen if you change to a lower gear while you're going too fast?
Question 10
1The vehicle could jack-knife
2The engine could stall
3The brakes could fail
4The trailer could uncouple
Show the answer
The vehicle could jack-knifeRightThis was the right answer
Severe braking or selecting a gear too low for your road speed can cause the tractor unit to slow more quickly than the trailer. The trailer can then pivot around the coupling (fifth wheel), causing the vehicle to jack-knife. Jack-knifing is more likely to occur with an unladen vehicle, particularly on a bend or curve.
When is an articulated vehicle most at risk of jack-knifing?
Question 11
1When it's fitted with an endurance brake (retarder)
2While it's manoeuvring slowly
3While it's under heavy braking
4When it's fully loaded
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While it's under heavy brakingRightThis was the right answer
Heavy braking can cause an articulated vehicle to become unstable and may even lead to jack-knifing; this is more likely to occur when the trailer is unladen.
You use a manually selected axle differential lock to escape a slippery patch. Which instruction should you follow when returning to normal grip?
Question 12
1Only after selecting top gear
2Once the engine has warmed up
3Disengage it promptly when normal grip is restored, following the vehicle handbook
4As soon as the snow has cleared
Show the answer
Disengage it promptly when normal grip is restored, following the vehicle handbookRightThis was the right answer
A selected differential lock helps traction on poor surfaces but can increase understeer. Disengage it when the poor conditions end, following the vehicle-specific procedure. Movement alone is not a universal instruction to switch it off; never assume all locking systems operate identically.
A compatible legacy tractor has red, yellow and blue brake airlines and the trailer has only red and yellow couplings. Which line needs the manufacturer’s separate instruction rather than a connection to that trailer?
Question 13
1Red
2Yellow
3Black
4Blue
Show the answer
BlueRightThis was the right answer
The blue auxiliary line needs the tractor manufacturer’s instruction. Do not improvise: incorrect handling can make the combination dangerous.
Your lorry is equipped with anti-lock brakes. What's the correct procedure for stopping in an emergency?
Question 16
1Apply the footbrake firmly in a pumping action until the vehicle has stopped
2Apply the footbrake firmly and continuously until the vehicle has stopped
3Apply the footbrake and handbrake until the vehicle has stopped
4Apply the handbrake only
Show the answer
Apply the footbrake firmly and continuously until the vehicle has stoppedRightThis was the right answer
With ABS, press the service brake firmly and continuously in an emergency, following the handbook. Do not pump the pedal. ABS helps retain steering control but does not justify following closely or braking late; never assume it will shorten the stopping distance.
What does changing to a lower gear on a long downhill gradient help to avoid?
Question 17
1Brake fade
2Clutch slip
3Excessive engine revs
4Tyre wear
Show the answer
Brake fadeRightThis was the right answer
Engaging a lower gear and using engine braking will help you to control your speed as you're going downhill. This reduces the demands on the brakes, and helps to prevent them from overheating. This will reduce the likelihood of brake fade.
You have to drive onto a muddy building site. Why should you switch on your diff-lock?
Question 18
1To make your steering lighter
2To improve your fuel consumption
3To increase your engine power
4To make the wheels less likely to spin
Show the answer
To make the wheels less likely to spinRightThis was the right answer
Engaging the diff-lock means that the driven wheels are locked together. This reduces the likelihood of wheel spin. Remember to switch off the diff-lock as soon as you're on firm ground again, otherwise you could damage the transmission.
How will anti-lock brakes improve your vehicle's safety?
Question 19
1They allow you to follow other vehicles more closely
2They help you keep steering control while braking heavily
3They let you drive faster on wet roads
4They enable you to brake later than normal
Show the answer
They help you keep steering control while braking heavilyRightThis was the right answer
When your steering wheels are locked - as can happen in a skid - you can't steer the vehicle. Anti-lock brakes help you to keep steering control while you're braking heavily, but they aren't a substitute for good forward planning. Anticipation and planning ahead will minimise the risk of skidding more effectively than relying on your braking system.
What could prevent air pressure from building up in an air-brake system in frosty weather?
Question 20
1Moisture in the air may form bubbles in the brake fluid
2The air will contract, reducing the pressure
3The dampness may cause valves to rust
4Moisture drawn in with the air may freeze and cause a blockage
Show the answer
Moisture drawn in with the air may freeze and cause a blockageRightThis was the right answer
Moisture in the air system can freeze and obstruct valves or pipes. Where fitted, the air dryer removes moisture between the compressor and reservoirs, not before compression. Maintain the dryer and drain arrangements to the manufacturer’s instructions; do not drive with unsafe brake pressure.