Most drivers don't understand what many of our most common road signs mean, according to a survey by the road-safety charity Brake.
It found that the zebra crossing symbol is a mystery to 67% of the population, while half do not recognise the no-vehicle sign - and a third are flummoxed by minimum-speed displays.
Meanwhile, 15% of the 2,050 people polled failed to recognise the national speed limit, and only 12% could identify all eight of the signs they were shown.
The elderly who passed their tests when they were 17 are particularly at fault, says Brake, because it is likely that they have never opened the Highway Code since.
Said spokeswoman Katie Shephard: "This means that 55-year-olds have been driving a shocking 38 years without refreshing their knowledge about the rules of the road.
"This is leading to a dangerous lack of knowledge in drivers. Driving is one of the most hazardous things that people do on a daily basis, and we urge all drivers to refresh their knowledge of the Highway Code to help keep themselves and others safe."
Copyright © Press Association 2009