Contrary to current thinking, new research suggests that using hands-free mobile phone systems in cars may not be safe.

The results of a study on the brain's ability to process two cognitive tasks simultaneously appears to prove that hands-free use of cell phones while driving impairs a driver's ability to perform at 100 percent. Cognitive, as opposed to sensory, tasks are those that require high levels of thinking.

PC Advisor's story last week broke the news that Rospa (the Royal Society for the Prevention of Accidents) is strongly in favour of banning phone use in cars, and berated the government for lack of research in the area.

Now an American study, Interdependence of Nonoverlapping Cortical Systems in Dual Cognitive Tasks, conducted by researchers at the Center for Cognitive Brain Imaging at Carnegie Mellon University in Pittsburgh and commissioned by the Air Force Office of Scientific Research, has found further backing to Rospa's argument.

Head of the research team, Dr Marcel Just, believes the implications of the study reach well beyond the laboratory.

"It should be part of the education of every driver and part of police licensing procedures to make it clear that demanding driving can't be safely time-shared with other tasks," Just said.

Just included that not only mobile phone usage, with or without headsets, but also conversations and the radio should be stopped in tough driving situations. This may sound draconian, but this is the first study of its kind that measures if a person can do two high-level tasks at the same time, said Just.

"People think of various parts of the brain as functioning autonomously. [But in our research] you see this interdependence and resource dependence," Just said.

In the test for visual tasks, which would be similar to driving, there was an increase in the error rate when the volunteers performed dual versus single tasks as well as an increase in response time.