LGV Braking Systems 2

Question 1

What is the correct procedure if the low air pressure warning activates while driving?

Accepted Answer

Stop as soon as safely possible, do not continue driving until the fault is identified and fixed

Answer

If the low air pressure warning activates, the driver must stop as soon as safely possible. Continuing to drive with low air pressure risks total brake failure and the automatic application of spring brakes at speed, which could cause loss of control.

Question 2

What is anti-compound on a braking system?

Accepted Answer

A mechanism that prevents the service brake and spring brake from being applied simultaneously on the same wheel

Answer

Anti-compound prevents the simultaneous application of both the service brake and spring brake on the same wheel, which could generate excessive force and damage brake components. When the parking brake is applied, the anti-compound device releases the service brake pressure.

Question 3

What should a driver check regarding brakes during a daily walkaround?

Accepted Answer

Air pressure build-up rate, warning devices, air leaks (listen), brake hose condition, and brake disc/drum condition

Answer

During the daily check, the driver should verify that air pressure builds up correctly, warning devices function, there are no audible air leaks, brake hoses are not damaged or chafing, brake discs/drums are not excessively worn or cracked, and the handbrake holds the vehicle.

Question 4

What is the purpose of the trailer emergency line (red coupling)?

Accepted Answer

To automatically apply the trailer brakes if the trailer separates from the tractor unit

Answer

The emergency line (red coupling head) maintains air pressure in the trailer's emergency relay valve. If the trailer separates from the tractor, this line loses pressure, causing the emergency relay valve to apply the trailer brakes automatically, bringing the trailer to a halt.

Question 5

What is brake hysteresis?

Accepted Answer

The difference between braking force during application and release — important for smooth, controlled braking

Answer

Brake hysteresis is the difference between the braking force during brake application and during brake release at the same pedal pressure. Good hysteresis provides smooth, progressive control. Poor hysteresis causes 'snatchy' brakes that are difficult to modulate.

DVSA UK Driving Theory Practice Test

DVSA UK Driving Theory Practice Test

LGV Braking Systems 2