“Keep Left Unless Overtaking” say the signs. It’s a simple instruction that should be easy to obey. So why do so many drivers struggle with the concept?

Keeping to the left on multi-lane roads is the safest way to travel because it means that all overtaking is done on the right. This gives the driver being overtaken better vision of cars coming past them, therefore minimising the risk of them moving over at the wrong time. It also smoothes the traffic flow as all the slower cars are travelling in line, with the faster ones in a separate group.

You seldom see any problems if there are two traffic lanes each way on motorways, the great majority of drivers do the right thing and conscientiously use the left lane. But give them three lanes and for some reason it all falls to pieces. An amazing number of people ignore the left lane and cruise in the next one out.

Even worse, if there are four lanes many drivers refuse to travel in the first two and insist on routinely cruising in the third lane out. This bizarre situation is a common sight on the M1 where it travels between the Gold Coast and Brisbane.

On a three-lane motorway a driver doing the right thing and travelling in the left lane has to change lanes no fewer than four times to safely overtake a single vehicle. On a four-lane motorway it can be necessary to make a ridiculous six lane changes. A potentially dangerous situation.

If you ask them (very politely) why they don’t use the left lane, they appear to think that keeping left simply means not using the extreme right-hand lane. The doesn't make sense and leads to the constant weaving in and out of traffic that can be so hair-raising on Australian motorways.

The slower drivers often blame the faster ones for this excessive lane changing and for overtaking on the inside. But the fault frequently lies with the slow guys being in the wrong lanes.

A complaint from the slower drivers is that they hate other drivers overtaking their car on the left. However, guys and gals, it’s simple to stop that from happening – keep left unless overtaking and it’s then impossible for anyone to overtake you on the left.

By the way, keeping to the left isn’t only safer on motorways it also makes for better safety and traffic flow on normal multilane roads in all other areas, even around the suburbs.