Dangerous to talk while driving - even handsfree

Drivers who talk on a cellphone - even one that's hands-free - while executing a left-hand turn at an intersection could be putting themselves at serious risk, say neuroscientists.

Most serious traffic accidents occur when drivers are making a left-hand turn at a busy intersection. When those drivers are also talking on a hands-free cell phone, "that could be the most dangerous thing they ever do on the road," said Dr. Tom Schweizer, a researcher at St. Michael’s Hospital.

Immersing a driving simulator with a fully functional steering wheel and pedals in an MRI allowed researchers to map in real time which parts of the brain were activated or deactivated as the simulator took them through increasingly difficult driving maneuvers.

The researchers were able to show for the first time that making a left-hand turn requires a huge amount of brain activation and involves far more areas of the brain than driving on a straight road or other maneuvers.

When the drivers were also involved in a conversation, the part of the brain that controls vision significantly reduced its activity as the part that controls monitoring a conversation and attention was activated.

The research was published online on February 28, 2013 in the open access journal, Frontiers in Human Neuroscience.

Visually, a left-hand turn is quite demanding," Dr. Schweizer said. "You have to look at oncoming traffic, pedestrians and lights, and coordinate all that. Add talking on a cell phone, and your visual area shuts down significantly, which obviously is key to performing the maneuver."