Before anyone in the UK can take their practical driving test, they must first pass a theory test. This includes learning about the laws of the road, understanding road signs, and completing a hazard perception test. However, despite this requirement, many motorists appear to have forgotten the meaning of one common but very important road sign. The sign in question is circular, with a white background and a thick black diagonal stripe across the middle.

This sign is the national speed limit sign, yet it seems to confuse a large number of drivers. A Reddit thread revealed just how widespread the misunderstanding is, with one user jokingly claiming that “99% of drivers don’t know what this sign means.” Many people jumped in with humorous guesses, suggesting everything from a “national drifting zone” to a free pass for BMW drivers to speed and ignore indicators. Others joked that it was an invitation to “go as fast as you want” or “drive in the countryside.”

In reality, the sign indicates that the national speed limit applies on the road ahead, replacing any previous temporary restrictions. According to the RAC, this means that in built-up areas with street lamps closer than 200 yards apart, the limit is 30 mph. On single carriageways, it rises to 60 mph for cars but drops to 50 mph for vans or vehicles towing caravans or trailers. On dual carriageways and motorways, the limit is 70 mph for cars and 60 mph for larger vehicles or those towing.

Importantly, while the national speed limit sets a maximum, it does not guarantee that driving at that speed is always safe. Conditions such as heavy traffic, poor weather, or winding roads may require drivers to go slower. The RAC advises that motorists should always use their judgment, remembering that speed limits are a maximum, not a target. So, while the sign itself is straightforward, the safe application of it depends entirely on awareness, responsibility, and common sense behind the wheel.