One in ten over-65s don't know the UK motorway speed limit, according to a new survey carried out by the AA Charitable Trust.
8% of drivers asked - the equivalent of 250,000 UK drivers - got the limit incorrect when answering the survey. 7% of respondents believe it is 80mph, and 1% believes it is 60mph.
Men were twice as likely as women to say the limit is 80mph, and Scotland was the worst region for incorrect guessers.
The 18-24-year-old age group proved the best at identifying motorway speed limits, with 95% answering correctly compared to just 89% of over-65s.
The survey coincides with Channel 5's new series of Dangerous Driver's School – where terrible drivers are specially trained to be more competent on the roads – with the AA Charitable Trust giving away 2,000 free driving courses to mark the show's release.
Edmund King, director of the AA Charitable Trust, said: "It is astonishing that 250,000 qualified drivers don't seem to know the motorway speed limit is 70mph. Some confusion about the motorway speed limit for cars could well be down to the previous Transport Secretary floating the idea of raising the limit to 80mph."
The lack of knowledge around limits highlights the importance of keeping your driving skills up to date. This follows a previous AA study that showed that some 17 million drivers might struggle retaking their driving test.