Braking Systems & Vehicle Handling

What causes brake fade when descending a long, steep hill in a heavy lorry?

• AThe brake linings freezing to the drums in cold weather during a long descent
• BOverheating of the brakes from prolonged use, reducing their effectiveness✓
• CExcessive air pressure building up in the braking system throughout a long descent
• DThe tyres losing tread depth and gripping the road surface less on the descent

Answer: Continuous use of the footbrake on a long descent overheats the brakes and reduces their effectiveness, a condition known as brake fade. Selecting a lower gear and using an endurance brake helps control speed without overheating.

What is the main purpose of an endurance brake (retarder) on a lorry?

• ATo help control speed on long descents and reduce wear on the main brakes✓
• BTo replace the parking brake when the vehicle is left standing on a gradient
• CTo increase the engine's maximum top speed
• DTo warm the brakes and tyres up before the start of a long motorway journey

Answer: An endurance brake or retarder slows the vehicle without using the wheel brakes, helping to control speed on long downhill gradients. This keeps the main brakes cool and reduces the risk of brake fade.

You start the engine and the air-brake low-pressure warning is showing. What should you do?

• ADrive off slowly until the warning clears
• BIgnore it, because the warning always clears on its own once the vehicle is moving
• CWait until the air pressure has built up to the correct level before moving off✓
• DPump the footbrake repeatedly while driving

Answer: You must not move off until the air pressure has built up enough for the warning to stop. Driving with low air pressure means the brakes may not work effectively.

Why should a driver brake earlier and more gently in a fully laden lorry than when it is empty?

• AThe extra weight greatly increases the stopping distance✓
• BThe braking system is deliberately weakened when the vehicle is fully loaded
• CThe speed limiter stops working once the vehicle is carrying a full payload
• DLoaded vehicles are not fitted with anti-lock braking of any kind by law

Answer: A laden lorry has much greater momentum, so it needs a far longer distance to stop. Braking earlier and progressively keeps the vehicle stable and avoids harsh stops.

How does an anti-lock braking system (ABS) help when you brake hard?

• AIt helps you keep steering control by stopping the wheels from locking✓
• BIt applies the trailer brakes before the tractor brakes when you stop
• CIt halves the stopping distance on wet, dry and loose road surfaces
• DIt lets you follow closer, because the lorry can stop as quickly as a car

Answer: ABS prevents the wheels locking under heavy braking, so you can still steer. It does not remove the need for a safe following distance, and stopping distances can still be long, especially on loose or wet surfaces.

The ABS warning light stays on after you have moved off. What should you do?

• ACarry on as normal, as the light is just a service reminder
• BHave the system checked, as the ABS may not be working✓
• CPump the brake pedal hard until the light goes out on its own
• DSwitch off the ignition while moving to reset the ABS unit

Answer: The ABS warning light should go out once the vehicle moves off. If it stays on, the system may have a fault and must be checked; the brakes may still work but without anti-lock protection.

According to the Highway Code, how much longer can stopping distances be on icy roads than on dry roads?

• AUp to ten times longer✓
• BUp to twice as long
• CUp to four times longer
• DUp to fifteen times longer

Answer: The Highway Code advises that the gap should be at least doubled on wet roads and increased up to ten times on icy roads, because stopping distances can be that much greater.

What is the most common cause of an articulated lorry jack-knifing?

• ASelecting a lower gear before a long downhill section
• BUsing the endurance brake gently on a long straight descent
• CHarsh braking, especially on a bend, causing wheels to lock✓
• DDriving with the trailer loaded evenly across all its axles

Answer: Jack-knifing usually follows harsh or late braking, particularly on a bend or slippery surface, when the tractor's wheels lock and the trailer pushes the unit round. Plan ahead and brake early and progressively.

Why should you take care using an endurance brake (retarder) on a slippery road?

• AIt switches off the ABS, so the service brakes cannot be used
• BIt stops working when the road surface is wet or icy
• CIt increases the load on the front axle and overloads the tyres
• DIt can make the drive wheels lose grip and the vehicle skid✓

Answer: An endurance brake acts on the drive axle. On slippery roads the braking effect can make the drive wheels lose grip, so it should be used with care or switched off in those conditions.

Why should you not coast downhill with the gears in neutral or the clutch held down?

• AIt makes the air system build pressure far above the safe level
• BIt switches off the lights and indicators on many heavy vehicles
• CYou lose engine braking, so the brakes may overheat and fade✓
• DYou gain extra engine braking, which could make the trailer skid

Answer: Coasting removes engine braking and reduces control. Relying on the footbrake alone on a descent can overheat the brakes and cause brake fade.

When approaching a bend in a heavy lorry, when should you brake?

• AIf the bend has a warning sign with a speed shown
• BAfter the bend, so the load does not move on the turn
• CIn the middle of the bend, once you can see the exit
• DBefore the bend, while travelling straight and upright✓

Answer: Braking should be done before the bend while the vehicle is straight. Braking on a bend can unsettle the vehicle and increase the risk of skidding or rolling over, especially with a high load.

On high-speed roads in dry conditions, what minimum gap does the Highway Code advise between you and the vehicle in front?

• AAt least a two-second gap✓
• BAt least a half-second gap
• CAt least a car's length
• DAt least a one-second gap

Answer: The Highway Code advises at least a two-second gap on high-speed roads and in tunnels, and at least double that in wet conditions. A heavy lorry often needs more.

In strong crosswinds on an exposed road, which vehicle is most at risk of being blown off course?

• AA fully laden low-loader carrying a machine
• BAn empty high-sided lorry or curtain-sider✓
• CA tanker lorry filled to its maximum weight
• DA tipper lorry carrying a full load of stone

Answer: High-sided vehicles present a large side area to the wind, and when empty they have less weight to resist it. Plan routes and reduce speed when high winds are forecast.

On a lorry fitted with spring parking brakes, what happens if the air pressure is lost completely?

• AThe engine stops, but the brakes stay released
• BThe spring brakes apply and hold the vehicle✓
• CThe brakes release and the vehicle can roll away
• DThe service brake works normally until refilled

Answer: Spring brakes are held off by air pressure. If the pressure is lost, the springs apply the brakes, which is why a vehicle with a serious air leak may stop and be unable to move.