At first glance, it looks like just another round white road sign with a black stripe running across it. Simple, right? But one motorist recently went viral after claiming that “99% of drivers don’t actually know what this sign means” — and the truth has left many shocked.

This mysterious road sign is officially called the National Speed Limit sign. It doesn’t tell you a number — instead, it tells you to follow the default speed limit for that type of road.

• On single carriageways, the national limit is 60 mph.
• On dual carriageways and motorways, it’s 70 mph.
• For vans and certain vehicles, the limits are slightly lower.

Many drivers wrongly assume the sign means “no speed limit” or “drive as fast as you like,” which can lead to dangerous mistakes on the road. In reality, it’s one of the most important signs to understand — especially outside built-up areas where limits aren’t clearly marked.

Closing Punch

So the next time you see that plain white circle with the black stripe, remember: it’s not just a blank sign. It’s the law telling you to know your limits — literally. And it turns out, far more drivers are clueless about it than you might think.