Cluttered groups of road signs are more of a danger than driving on drugs.

A King’s College psychiatrist has said: “An information overload can harm concentration more than marijuana, with men twice as likely to be distracted as women. Information overload can also reduce a person’s ability to focus as much as losing a night’s sleep.”

The findings were supported by the RAC Foundation this week, at the Institute of Highways and Transport driver information conference in London.

Edmund King, RAC Foundation executive director, said at the conference: “Signs that are clear, concise, relevant, reliable and timely can improve safety and reduce the number of drivers who get lost each day. Conversely clutters of contradictory signs lead to confusion that can result in collisions.”

“Driving in a rural area with traffic news on the radio, instructions from satellite navigation, over complex road signs with four different messages, means people may miss the ‘flood’ sign’,” said an RAC motoring psychologist.

King said road authorities can play their part by ensuring that road signs spring no surprises and do not contribute to confusion.