The research relied on 12 volunteers who completed a series of driving tasks on two different days. The study assessed their braking, reaction time, speed deviation and lane changes. On one day the volunteers were asked to drive under four conditions: no phone use, simple conversation over a hands-free device, deep conversation over hands-free device and text messaging.
The next day the same volunteers were asked to drink alcohol to reach three specific BAC levels: 0.04, 0.07 and 0.10. The results revealed that the driving skills of volunteers declined equally among those who were 25% above the legal limit (0.10) and those who used their phone to text message. The study found that those using hands-free phones for simple conversations had a comparable BAC of 0.04 while those engaged in more involved conversations drove as if they had a BAC of 0.07.
The study concluded that even the use of hands-free devices can put drivers and others on roadways at risk of injury or death by causing distracted driving accidents. Making calls by themselves does not appear to be the problem, as simple conversations did not lead to a dramatically increased risk of trouble. Instead, it’s those conversations that are especially cognitively demanding, whether by phone or text, that represent real worries.