Do You Actually Know What This Road Sign Means? The Truth May Surprise You

Devon and Cornwall Police’s Road Safety Team has shared a breakdown of the meaning behind one of the most familiar signs on the road, and it turns out many drivers may not know the full story.

Where the Sign Came From

The team explained that the National Speed Limit sign, a white circle with a black diagonal line, dates back to the 1934 Road Traffic Act. That act brought in a 30 mph limit for built up areas, which meant a new sign was needed. At the time, the sign was designed to mean no speed limit or derestricted.

According to the explanation, the white circle was intended to resemble a streetlamp with a black line through it. The idea was simple. No streetlights meant no limit.

How It Became the National Speed Limit Sign

In 1965, a 70 mph limit was introduced on roads that had previously been unrestricted. Rather than create a new sign, the existing derestricted sign was reused to show the new National Speed Limit.

The appearance stayed the same, even as rules changed again in the 1970s, when the limit on single carriageways for cars was amended to 60 mph. Dual carriageways and motorways remained at 70 mph for cars.

What It Means Today

The team added that if you see a system of street lighting no more than 200 yards apart with no repeater signs, the limit is probably 30 mph in England unless signed otherwise. In Wales, this would be 20 mph. If you see repeaters on some lampposts or on the road surface, the posted speed applies.