Engaging the diff-lock means that the driven wheels are locked together. This reduces the likelihood of wheel spin.

You must always disengage the diff-lock as soon as the vehicle is moving. The differential allows the rear wheels to revolve at different speeds, and this allows the vehicle to follow a curved path.

Attempting to turn with the diff-lock engaged could result in the vehicle continuing straight on.

It’s important to check all fluid levels during your daily checks, but it’s especially important to remember the hydraulic fluid reservoir. A loss of fluid could lead to brake failure.

If a warning buzzer or light alerts you to a loss of air pressure, you should stop on the side of the road immediately. You should have enough air in reserve to allow you to do this safely. Don’t start or continue your journey until the fault has been repaired.

If the brake pedal is hard to press, this could mean a loss of vacuum or a fault in the vacuum pump. You shouldn’t drive the vehicle until the fault has been repaired.

A loose brake pedal would suggest a serious loss of fluid from the hydraulic system. Don’t drive your vehicle until the fault has been checked and fixed by a qualified person.

In frosty weather, to prevent moisture from freezing in the air-brake system, you should make sure that you drain the air tanks daily. Most modern vehicles have an automatic draining system, which should be checked regularly.

When air is compressed, moisture condenses and collects in the air tanks. This can find its way along the network of pipes connected to the brakes. In frosty weather, the moisture can freeze in the pipes, blocking them completely.

An endurance brake or retarder, as it is commonly known, is a system for controlling the vehicle’s speed without using the footbrake. It replaces some of the functions of friction-based brakes, which are susceptible to brake fade on long downhill slopes.

The endurance brake (retarder) usually operates by applying resistance, via the transmission, to the vehicle’s driven wheels. If the road is slippery, the tyres may lose grip, and the wheels will lock.

By using a retarder, the life of the brake linings is extended. This is because a retarder works by slowing the vehicle without using the wheel-mounted brakes.