Is it illegal to drive 'too slowly' in Australia?

For many motorists, there are few things more frustrating than being caught behind someone who, for reasons known only to them, has decided to travel even just 10km/h below the speed limit.

The bad news is that In most parts of Australia, there isn’t a specific law that forbids driving 'too slowly' – nor are there any minimum speed thresholds at which you’re allowed to travel.

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However, driving significantly below the speed limit can be deemed an offence under Australian Road Rule 125.

The rule states: “A driver must not unreasonably obstruct the path of another driver or a pedestrian” – with the following provisos: “For this rule, a driver does not unreasonably obstruct the path of another driver or a pedestrian only because:

1. The driver is stopped in traffic; or
2. The driver is driving more slowly than other vehicles (unless the driver is driving abnormally slowly in the circumstances).

It then gives the following example:

“A driver driving at a speed of 20 kilometres per hour on a length of road, to which a speed limit of 80 kilometres per hour applies, when there is no reason for the driver to drive at that speed on the length of road.”

That is indeed significantly below the speed limit, and certainly much rarer than the common-enough sight of a car travelling 10- or 15km/h below the posted limit. So, in most cases, it's not a very useful law.

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While it’s clear that driving too slow and obstructing traffic behind you is an offence...

The word “unreasonable” allows for discretion for those who may have a reason to be going slowly – such as inclement weather, travelling past an accident scene, animals on the road, or mechanical issues where it’s unsafe to stop.

The law can also be used against drivers who hog the right lane on a freeway, even if they’re travelling only a few km/h below the speed limit. When was the last time you saw that law actioned?

Of course, it also allows for someone to drive as slowly as they want if they’re not obstructing traffic.

“If you are going 50km/h down the Monash Freeway at 1am with no cars on the road, it’s not a drama,” Victoria Police Highway Patrol inspector Simon Humphrey told News Ltd. “But if you are doing that speed at 7am, in the right-hand lane, during peak hour – it might be a problem.

“It’s about common sense. It’s about obstruction rather than speed.”

So, in short, use common sense and think of other drivers.

And remember, even if someone is breaking Rule 125, it doesn’t excuse you from breaking Rule 126: the one against tailgating.

“A driver must drive a sufficient distance behind a vehicle travelling in front of the driver so the driver can, if necessary, stop safely to avoid a collision with the vehicle.”