Britain's motorways "remain a mystery" for many drivers as 19 million people live in areas without the 70mph roads, a motoring group has warned.
The RAC Foundation called for motorways to be designed for drivers who rarely use them after Press Association analysis of Department for Transport data revealed that 89 local authority areas are not covered by the motorway network.
The motoring research charity's director, Steve Gooding, said: "While one in five miles driven by car takes place on a motorway, for many motorists these roads remain a mystery.
"The challenge is to make motorways as welcoming and safe as possible, so those people who only use them once in a blue moon feel comfortable doing so."
Transport Secretary Chris Grayling announced plans last month to allow learner drivers on motorways to better prepare them for independent driving after passing the test.
AA president Edmund King said: "One of the features this new research reveals is the wisdom in making the proposed motorway element of driver training voluntary.
"With nearly 30% of the population without a motorway in their area, making it compulsory would make it difficult for learners in the Highlands, the West Country and other rural areas to pass their test.
"If they move to another part of the country where they need to go on a motorway, the opportunity to get a familiarisation course is still available to them."
A Highways England spokesman said: "Over the past 18 months we have delivered a number of campaigns to help drivers travel confidently and safely on our motorways.
"Our traffic officers and information line are also available to help drivers 24/7."