It has long been assumed that using a mobile device while driving is distracting because drivers were looking at their phones and not the road. Come up with a way to keep the driver's eyes on the road, the reasoning went, and you've solved the problem.
So when manufacturers came up with various hands-free features for smartphones, it was generally thought drivers could safely drive and talk. But safety experts have pointed out all along that taking your eyes off the road isn't the only distraction.
When you carry on a conversation while driving, they point out, your mind has to divert at least some attention to what you are saying and hearing. Even if your eyes never leave the road, the data they process is at least partially degraded by the attention given to the conversation.
But if that is true, wouldn't a conversation between a driver and a passenger in the car be just as distracting?
Testing the theory
Researchers at the University of Illinois decided to find out. They used a driving simulator and videophone to assess how a driver's conversation partner influences safety on the road.
"We've done years of study on driver distraction, and previous studies suggest that passengers often aren't distracting. In fact, passengers can be helpful, especially if they're adults who have had experience and also are active drivers themselves," said University of Illinois psychology professor Arthur Kramer.
The study used 4 scenarios: a driver alone in the simulator, a driver speaking to a passenger in the simulator, a driver speaking on a hands-free cellphone to someone in a remote location, and a driver speaking on a hands-free cellphone to someone in a remote location who could see the driver and observe the driving scene out the front windshield via videophone.
Using college students as their subjects, the researchers devised a fairly challenging highway scene that involved merging and navigating around unpredictable drivers in other cars. They noted the study drivers' lateral moves, distance from other cars, speed, collisions, and ability to find and take a designated exit.
"We also recorded their speech as they talked to their partner in three out of the four conditions, and we looked at where they looked – we had an eye tracker built into the simulator," Kramer said. "So it was a pretty rich data set."
The results were pretty much what you would expect. Driving alone was the safest option. No distractions. While having a passenger helped here and there – they helped locate exits and road signs – overall they proved to be a negative.
As you might imagine, carrying on a cellphone conversation while driving was the most dangerous of the tests. Talking to someone who had no awareness of what was going on inside or outside the car more than tripled the likelihood of a collision, the researchers found.
The only real surprise involved the fourth driving scenario – when a driver spoke to someone who was not in the car but who could observe the driver's face and the view out the front windshield on a videophone.
"Drivers were less likely to be involved in a collision when their remote partner could see what they were seeing," said John Gaspar, one of the researchers. "And this benefit seems to be driven by changes in the way partners talked to the driver."
The findings suggest having a conversation can actually improve the safety of the driving experience, so long as the conversation partner knows what's going on in the car and sees what the driver sees.
Again, it's safest to drive alone. But having a system that provides a video feed of the roadway seems to make accidents less likely. If the conversation partner knows what's going on in the car, he or she can stop talking or draw the driver's attention to specific road conditions.