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What does rule 108 entail?

This rule states that when driving a truck or bus on a route marked "trucks and buses must use low gear," you should proceed in an apparatus low enough to restrict your vehicle's speed without applying the brake pedal. You must reduce your speed and shift to a low gear while Road Rule 108 is in force. This will put the truck in the proper gear for the descent and eliminate the need to apply the foot brake. The engine or exhaust brake should be used to properly regulate the truck throughout the descent. When you see a particular sign that says "trucks and buses must utilize low gear," that's when Road Rule 108 kicks in. Before you approach a dangerous descent, these signals will surface. In many cases, the indicator will also indicate how long the conditions will remain.

The Road Rule may apply for several meters in specific instances. All truck and bus drivers on Australian roads equipped with a 'lorries & buses need to use lower ratio' signage that are required by law to follow this rule. Keep an eye out for caution signs indicating steep descents, such as those found on the South Eastern Freeway in Adelaide. The South Eastern Freeway; Willunga Hill; Main South Road, O'Halloran Hill; Old Belair Road, Mitcham; James Road, Mitcham; Ocean Boulevard, Seacliff Park have all received Rule 108 signs.

If the sign does not specify the duration of the relevant highway, you must follow Road Rule 108 until you encounter a second sign indicating the end of the truck and bus low gear region.


  • If you lose control of your lorry or carriage on an uphill road, the consequences could be deadly; you could brutally murder yourself or others. Serious consequences may also be imposed.

  • Trucks and buses must commute at a moderate speed the entire way down an inclined road when descending. This is something that foot brakes can't accomplish on their own.

  • These brakes can easily combust and forfeit their effectiveness, resulting in a loss of vehicle control.

  • The brake linings can lose their grip and you can lose control if you apply the foot brake or don't use a low adequate transmission to slow down the car.

How to safely descend-

You must begin decelerating and swapping to a low gear as soon as you see the 'trucks and buses must use low gear' sign. This tends to mean you won't need to use the foot brake when travelling down the hill because you'll be in the proper gear before starting to descend. You must use the power unit or combustion break the entire way down the hill as you descend. This will help you maintain control and escape danger. Each car is unique. It's never a good idea to drive a truck or a bus without first learning how their braking systems work.

Penalties for failing to follow Road Rule 108-

If you fail to follow Road Rule 108 while driving your truck in South Australia, you may face a variety of fines. It is sometimes possible to avoid punishment by paying a $348 expiation charge. You could also incur three speeding fines, which would remain on your licence history for up to three years. You may lose your licence for at least three months if you accumulate 12 or more penalty points. The goal of Road Rule 108 is to ensure that truckers can safely climb steep terrain. While driving in South Australia, all truck drivers must adhere to this law.

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