Demystifying the Mysterious Traffic
The Meaning Behind the UK’s “Mysterious” Speed Sign
If you’ve ever seen a white circle with a single black diagonal stripe and wondered what it means, you’re not alone.
That simple sign marks the national speed limit — a rule many drivers find confusing because it shows no numbers.
When you pass it, the default speed limit for that road type applies:
- 60 mph on single carriageways
- 70 mph on dual carriageways and motorways
For vans, lorries, or vehicles towing trailers, the limits are lower.
The sign only applies where no lower limit is shown, and drivers must still adjust for weather, traffic, and road conditions.
Going the full speed isn’t always safe, even if it’s legal.
So, when you spot that black diagonal stripe, remember —
it’s not a signal to speed up, but a reminder to follow the national rules and drive safely.
