A UK driver recently reignited debate online after pointing out that many motorists fail to recognize a very common road sign: the circular white one with a bold black diagonal stripe. Although it’s included in the theory test, drivers often forget or misinterpret its meaning, with some joking online that it stands for “go as fast as you want” or “national drifting zone.”

In reality, the sign marks the start of the national speed limit. It cancels any lower or temporary limits in place beforehand, but the exact limit depends on both the road and the type of vehicle. Despite this clear legal definition, its real-world use often leads to confusion and misuse.

For cars, the national limit is 60 mph on single carriageways and 70 mph on dual carriageways and motorways. For vans or vehicles towing trailers, the limits are lower — 50 mph on single carriageways and 60 mph on dual carriageways or motorways. Built-up areas with regular street lighting remain at 30 mph unless otherwise marked.