Dyslexia, a reading and writing disorder, can slow a driver’s reaction time as much as drinking moderate amounts of alcohol, according to the results of a small study.

When Norwegian researchers compared how long it took drivers to react to road signs, they found that dyslexics were about 30 percent slower than other volunteers.

“Drivers just over the UK’s alcohol limit, which can be exceeded by drinking two pints of beer, are typically 10 percent slower than normal to react,” New Scientist magazine said.

Researcher Hermundur Sigmundsson and his colleagues at the Norwegian University of Science and Technology in Trondheim gave two simulated driving tests to 6 dyslexic volunteers and 11 other people. They were shown road signs as they drove on simulated country and city roads at different speeds.

In both tests, the dyslexic volunteers reacted slower than the other drivers.

“The results fit in with other studies which suggest that dyslexia may affect the way the brain processes sensory information,” according to the report.

About 10 percent of the population in Britain may have some form of dyslexia, which causes difficulty in reading, writing and spelling. It tends to run in families but scientists say environmental factors may also contribute to it. Other activities that delay driver reaction time, such as drinking and talking on a mobile phone, have been outlawed in Britain.

But the researchers said larger studies are needed to confirm their results before any action is considered.

Britain’s Department of Transport agrees. “Reaction time is only one of the cognitive functions needed for driving and it has not been consistently shown to be a good predictor of driving performance,” a spokeswoman told the magazine.