'99% of drivers' don't know what this road sign means

Knowing your road signs is an essential part of learning to drive. But one driver is convinced that there's very few of us that know what the meaning behind one in particular.

Passing your theory test is one vital cog in being able to legally get behind the wheel without an instructor next to you in the passenger seat. That's because it teaches you all the warning signs to watch out for, as well as vital information such as what speed limit signs mean.

Sure, even if you pass with flying colours, it does't make you a perfect driver by any means. Yes, we see you, the ones dubiously overtaking us despite us driving at the speed limit.

Basic limit signs aside (nothing too hard about numbers in a circle is there, really) those driving for a long time would be forgiven for not remembering what every sign means. And to be honest, I'm sure many would be lying if they could say they knew every sign when sitting the theory test in the first place.

But over on Reddit, one motorist has vented about one sign in particular. They reckon that many of us wouldn't be able to clock what it means at all.

What's the sign?

It's incredibly common and found on thousands of roads across the United Kingdom.

We're talking about the white circle with a diagonal black stripe through it at a 45 degree angle.

"I'm convinced 99% of drivers don't know what this sign means," the Redditor posted.

You will see this sign right across the country (Getty Stock Images)

What does it mean?

Replying on the Reddit thread, people had a good few guesses at what it might be. Joking, one wrote: "National speed limit, but what that limit is depends on what you’re driving. For example if you’re driving a BMW it’s 100mph and excuses you from using indicators."

Another said: "There's a road near me with this sign and if you're averaging more than 30mph down it you're either a complete plank or suicidal."

A third shared a rather worrying tale: "One of the girls at my old hairdressers genuinely thought it meant 'go whatever speed you want'."

The national speed limit is not the same everywhere (Getty Stock Images)

What does the official line say on the RAC?

The RAC website explains, saying: "A white circular sign with a single black diagonal stripe through it tells you that the national speed limit applies on the upcoming stretch of road. It supersedes any previous speed limit signs you may have had to adhere to, such as passing through temporary roadworks.

"Of course, even when the national speed limit applies, it might not always be safe to drive at that speed, so use your common sense on this."

So, while it says you can legally drive at 60mph, the law clearly states that it is first and foremost about being safe. That includes driving the speed of the traffic around you.

The national speed limit depends on the road you're on. It's 30mph in built up areas with street lights, unless you can see a sign stating otherwise.

On a single carriageway, it's 60mph for cars but 50mph for vans and anything bigger. The 50mph limit applies to cars towing something, too. On a dual carriageway and motorway, it's 70mph but 60mph for goods vehicles and cars carrying trailers or caravans.