According to the survey, three in five motorists thought a "be aware of cattle" warning sign indicated an area infected with foot-and-mouth disease.
The survey of 500 motorists - conducted to mark the 70th anniversary of the publication of the Highway Code - highlighted just how many people are still grappling with it.
According to the survey, three in five motorists thought a "be aware of cattle" warning sign indicated an area infected with foot-and-mouth disease.
Some drivers also thought the sign for a migratory toad indicates a French restaurant in the vicinity.
The executive director of the RAC Foundation, Edmund King, said: "The Highway Code is as much an essential road safety document for road users now as when it was published 70 years ago.
Best-seller
"Our survey would suggest that despite the Highway Code remaining one of the best-selling books, many motorists are unaware of the meaning of road traffic signs.
"The majority of motorists do not understand common warning signs. They clearly need to brush up their Highway Code knowledge."
The RAC stopped drivers in London and Glasgow earlier this month and asked them to identify specimens of road signs.
Only 10% of those asked recognised signs that a dual carriageway had ended, and 20% thought that those ordering them to give way to oncoming vehicles meant "one-way street ahead".
Five per cent said signs warning of side winds meant "kite flying area", while 50% did not recognise the sign indicating an end to a speed limit.
One reason for the poor results could be that more than two in three drivers admitted they had not looked at the Highway Code, published by the Driving Standards Agency, since taking their driving test.