Drivers who use hands-free electronic devices, as opposed to hand-held ones, are less likely to get into a crash, according to a study. With hands-free technology, drivers can make calls and perform a variety of other tasks while still keeping their hands on the wheel and eyes on the road.
"Any activity that places either visual or manual demands on the driver -- texting, browsing or dialling a hand-held phone, for instance -- substantially increases crash risk," said Tom Dingus, director of Virginia Tech Transportation Institute (VTTI) in the US.
"However, our recent study has found that the primarily cognitive secondary task of talking on a hands-free device does not appear to have any detrimental effects," Dingus said.
The goal of the project was to determine the extent to which crash risk could be affected by primarily mental behaviours, known as cognitive distractions.
Cognitive distractions occupy the mind but do not require the driver to look away from the road or remove their hands from the wheel, according to the study published in the journal Safety Science.
Examples include interacting with a passenger, singing in the car, talking on a hands-free cell phone, and dialling on a hands-free phone via voice-activated software.
Researchers used video and other sensor data from the Second Strategic Highway Research Program naturalistic driving study, the largest light-vehicle study of its kind ever conducted.
They analysed video footage of 3,454 drivers, 905 crashes -- including 275 more serious crashes -- and 19,732 control periods of "normal driving" for instances of cognitive distraction.
For comparison, they also studied examples of drivers performing visual and manual activities, such as texting on a hand-held phone or adjusting the radio.
Drivers who used a hand-held phone increased their crash risk by 2 to 3.5 times compared to model drivers, defined as being alert, attentive, and sober.
When a combination of cognitive secondary tasks was observed, the crash risk also went up, although not to nearly the same degree.
In some cases, hands-free cell phone use was associated with a lower crash rate than the control group. None of the 275 more serious property damage and injury crashes analysed were associated with the use of hands-free systems.
"There are a number of reasons why using a hands-free device could keep drivers more engaged and focused in certain situations," said Dingus. "One is that the driver looks forward more during the conversation. Although engaging in the conversation could cause a small amount of delay in cognitive processing, the driver is still more likely be looking in the direction of a precipitating event, such as another car stopping or darting in front suddenly," he said.
"The phone conversation could also serve as a countermeasure to fatigue on longer road trips. Perhaps most importantly, a driver who is talking on a hands-free phone is less likely to engage in manual texting/browsing/dialing and other much higher-risk behaviours," Dingus said.
"The research has shown consistently that activities requiring a driver to take his or her eyes off of the forward roadway, such as texting or dialing on a hand-held phone, pose the greatest risk," said Dingus.
"It is also important to note that in many newer cars, the driver can do some tasks hands-free using well-designed interfaces. Giving the driver an option to use a safer system will help with compliance for a new law and lead to fewer distraction-related crashes," said Dingus.