When talking or texting, drivers take longer to hit the brakes -- even if they're not hitting tiny keyboards, researchers at the University of Utah have found.
The researchers measured the effect on drivers' reaction time of performing seven different tasks in three situations: in the lab, in a driving simulator and in a moving vehicle. Additionally, in the moving vehicle, they evaluated drivers' attentiveness by recording whether they scanned for hazards at key intersections.
Talking on the phone, even hands-free, is more distracting than just listening to the radio while driving, they found. Most distracting of all, though, is responding to messages using a voice-controlled interface.
"Compared to other activities studied, we found that interacting with the speech-to-text system was the most cognitively distracting," wrote the researchers. "This clearly suggests that the adoption of voice-based systems in the vehicle may have unintended consequences that adversely affect traffic safety."
Their study, sponsored by the American Automobile Association's Foundation for Traffic Safety, was published Wednesday in a report entitled "Measuring Cognitive Distraction in the Automobile." The AAA has long campaigned for a blanket ban on texting while driving, and discourages drivers from talking on the phone, whether handheld or hands-free.
In a driving simulator, drivers took noticeably longer to hit the brakes when responding to messages through a voice-controlled interface, the study found. Talking, whether on the phone or to a passenger, also delayed braking, although not as much.
On the road, drivers were less likely to scan for hazards at intersections when talking, and least likely when dealing with messages.
One goal of the study was to create a standardized scale for measuring cognitive distraction, so that the effect of various activities in different environments can more easily be compared.
Starting with a value of 1 for performing a single task -- in this case, driving -- the researchers suggested that a maximum distraction of 5 was achieved by simultaneously driving, performing mental arithmetic tasks and memorizing a list of words. The most distracting real-world task, using a speech-to-text interface, scored 3.06. Listening to the radio was the least distracting task, at 1.21, followed by listening to audio books, at 1.75. Conversational tasks fell somewhere in the middle, with chatting to a passenger rating 2.33, chatting while holding a phone 2.45 and chatting on a hands-free phone 2.27.
Peter Sayer covers open source software, European intellectual property legislation and general technology breaking news for IDG News Service. Send comments and news tips to Peter at email@example.com.