This behaviour can be extremely risky, so we’ve made it easier to understand when it’s right to keep left, and when the rule doesn’t apply.

When the speed limit is above 80km/h

In South Australia, if the speed limit on a multi-lane road is higher than 80km/h or there’s a ‘keep left unless overtaking’ sign, you must drive in the left lane unless:

• overtaking a slower vehicle
• turning right or a making legal U-turn
• avoiding an obstruction or congestion.

Regardless of why you’re moving into the right lane, you must always check your side and rear view mirrors for a suitable gap in the lane next to you, and indicate for at least five seconds to give other road users enough warning of your intention to change direction.

Make sure there’s enough space before changing lanes. Remember, many newer vehicles have side mirrors that make vehicles appear further away than they really are, so it’s essential you check the internal mirror as well to ensure you don’t cut off the person in the next lane. Repeat the process when it’s safe to return to the left and don’t go over the posted speed limit.

Remember: you shouldn’t speed when overtaking vehicles.

Alarmingly, speeding when overtaking is a common – and potentially deadly – mistake. In fact, a 2019 RAA survey revealed 73% of motorists admitted to committing this offence regularly.

That’s why RAA Senior Manager Safety and Infrastructure, Charles Mountain, is calling for motorists to consider if staying in the right lane is the correct choice.

Increasing your speed over the posted speed limit to overtake a vehicle is a potentially dangerous move and also against the road rules.

If you’re caught speeding while overtaking, you might be hit with a speeding fine, or worse, charged with driving without due care, which can result in a court date.

The offence also carries a maximum $2500 fine, as well as a $94 Victims of Crime Levy and three demerit points.

That said, travelling excessively slow in the right-hand lane is also hazardous as you’re obstructing the flow of traffic. This offence can see you hit with a $125 fine, plus a $94 Victims of Crime Levy.

When the speed limit is 80km/h or below

If you’re driving along a road where the speed limit is below 80km/h, by law you can travel in any lane that’s available – left or right.

If the speed limit is 80km/h, you can travel in either lane unless there’s a sign stating: ‘Keep left unless overtaking’.

No lanes? No worries

Some suburban or regional roads don’t have any lanes or line markings. When there are no line markings, the rule of thumb is to imagine the left of the road as an imaginary line, keeping as far left as possible to allow traffic to flow smoothly around you.

Avoid travelling in the middle of the road if possible. If you do need to edge to the right, avoid lingering in the middle of the road for too long. Again, don’t forget to check your mirrors and indicate for at least five seconds before moving right.

Final word

By now you’ve probably noticed a consistent message pop up: stick left when possible. It helps traffic flow and allows other vehicles to safely overtake.

Why do we drive on the left? Well, that’s another story. Driving on the left-hand side dates back to when ancient Romans were conquering Europe. Intrigued? Read about the history of keeping left in our story Why do we stick to left side of the road?