Several Australian universities and the University of Barcelona measured the reaction capacity of 12 healthy volunteers who participated in a driving simulation test lasting two days, each a week apart.
Study co-author Sumie Leung Shuk Man of the University of Barcelona said the drivers took the test having consumed alcohol, and then using the cellphone. Habitual drinkers and those who had never consumed alcohol before the test were not allowed to participate.
"We conducted the study in Australia and the participants, who were volunteer students holding a driving license, had to keep their position in the center of the left lane on the screen at a speed of between 60 and 80 kilometers per hour, breaking every time a truck appeared," the researchers said in a statement.
"When the conversation using the hands free was simple, the effects were comparable to a blood alcohol content level of 0.04 gram per liter, which is below the legal limit of 0.5 g/l in countries like Spain and Australia. However, when more attention was required, their alcohol level analogue shot up to 0.7 g/l, which is above the legal limit in both countries yet below in other countries, such as the United States or Britain. When answering text messages, the rate stood at 1 g/l, which is illegal in any of all of these countries."
The findings suggest the use of hands free devices could also put drivers at risk, the researchers said.