Left-Hand Turns Most Dangerous Move on the Road: MRI Study

It’s common knowledge that distracted driving causes accidents, but given the summer’s increase in pedestrian and bike traffic in the city, it’s worth repeating. A Toronto MRI study published in early 2013 called Brain activity during driving with distraction: an immersive fMRI study revealed that left-hand turns use significantly more brain power than any other manoeuvre on the road. Add a distraction–such as an urgent conversation on a hands-free phone–and the brain is overloaded with information.

The study looked at 26 young adults, each of whom had been driving for an average of 7 years. The participants, which included 9 men and 7 women, underwent brain fMRI while performing a driving simulation exercise.

The participant’s brains showed minimal signs of activity when making right turns or simply driving straight, but left hand turns showed heightened brain activation. “Think about it. You’re in a busy intersection. You have to look at your own traffic light, to make sure you don’t turn on a red, and you have to look at the oncoming traffic to time your manoeuvre so you don’t get T-boned,” said Dr. Tom Schweizer, neuroscientist and lead author of the study.

Next, the researchers added distractions to the driving simulation: while the participants made left turns, they were asked a series of true or false questions via headset. What the researchers saw was striking: the visual posterior cortex, responsible for visual processing, shut down approximately 50 per cent, while blood moved into the prefrontal cortex, the part of the brain that governs decision making.

“Hands free is not brains free,” said Schweizer. “If you’re actively listening, you’re going to have to take some [brain] resources away from the primary task of driving.”

2014-07-08T21:33:26+00:00