A UK motorist recently sparked online debate by claiming that “99% of drivers” don’t understand a common road sign seen nationwide. The circular, white sign with a thick black diagonal stripe is often misinterpreted, despite being part of the mandatory theory test. Many drivers forget or misread its meaning after passing, leading to confusion on the roads.
Officially, this is the national speed limit sign, indicating that the legal speed limit from that point forward applies according to road type and vehicle category. On single carriageways, cars may travel up to 60 mph, while dual carriageways and motorways allow up to 70 mph. Vehicles towing trailers or larger vans have lower limits — 50 mph on single carriageways and 60 mph on dual carriageways and motorways.
In built-up areas with street lighting, the default speed limit remains 30 mph. Despite its clear definition, many drivers joke about the sign online, suggesting humorous interpretations like “go as fast as you want” or “national drifting zone.” Real-world driving often shows motorists ignoring limits, overtaking recklessly, or assuming the sign permits higher speeds.
Road safety experts emphasize that while the sign sets the maximum legal speed, conditions like traffic, weather, and road quality may require slower driving. Organizations such as the RAC remind motorists that safety and common sense should always take priority. This widespread misunderstanding underscores the importance of ongoing road education, even for experienced drivers, and highlights the gap between theory test knowledge and everyday driving behavior.