Chatting on a hands-free phone is more distracting to drivers than a conversation with a passenger, researchers have found. Drivers were more likely to drift out of their lane and miss a right turning if they were using a hands-free set, than if they were talking to someone sat in the car or not speaking at all, a study reveals.
The finding builds on recent work that suggests younger people's reactions become as slow as those of pensioners if they are talking on a hands-free set while driving.
David Strayer, at the University of Utah, used a driving simulator to see how conversations affected people's driving.
He asked 41 men and women to take part in 10-minute journeys during which they either chatted to a passenger, sat in silence with them, or drove alone but took a call from a person on a hands-free set.
Drivers had to negotiate two-lane roads with traffic moving in both directions, a multi-lane motorway, and were asked to take a specific exit to finish the test, according to the study in the Journal of Experimental Psychology.
"When there is a passenger in the car, almost everyone takes the exit, but half the people talking on the cell phone fail to," said Strayer. "A driver conversing with a passenger is not as impaired as a driver talking on a cell phone. You see bigger lane deviations for someone talking on a cell phone compared with a driver talking to a passenger," he added.
Analysis of the drivers' conversations revealed that they used more simple speech, with fewer syllables, when driving was more demanding.
The finding was significant enough for the researchers to urge people not to call drivers who would need to use a hands-free set to talk to them.
The risk of having an accident was greater if the driver was alone, the study found. "[If] the passenger is in the vehicle and knows what the traffic conditions are like, they help the driver by reminding them of where to take an exit and pointing out hazards," Strayer said.
A separate study commissioned by insurer RSA found that driving with a hangover is four times more dangerous than getting behind the wheel sober.
A poor night's sleep, low blood sugar and dehydration all affect the ability to drive safely, even if someone is within the drink-drive limit, the study by Brunel University found.
Students were tested on a driving simulator while sober and again while suffering a hangover. The tests were compared and it was found that, on average, hungover drivers drove almost 10mph faster, left their lane four times as often and committed double the number of traffic violations.
"What surprised us was that people were driving faster. The fact they were driving more erratically we'd expect. Not taking care, going through red lights, that's more alarming," Graham Johnston, an RSA director, said.
