Talking while driving is safest with someone who can see what the drive see, according to a recent study.

A new study from researchers from the University of Illinois at Urbana-Champaign offers fresh insights into how talking on a cell phone or to a passenger while driving affects one's performance behind the wheel.

"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," Arthur Kramer, who led the study, said in a statement.

For the study, Kramer and his team used a driving simulator and videophone to assess how a driver's conversation partner influences safety on the road. The researchers hoped to discover which aspects of talking to a passenger most affect a driver's performance -- rather than talking to someone on a cell phone, which is often dangerous. To do this, they set up four driving scenarios: a driver alone in the simulator, a driver speaking to a passenger in the simulator, a driver speaking on a hands-free cell phone to someone in a remote location, and a driver speaking on a hands-free cell phone to someone in a remote location who could see the driver and observe the driving scene out the front windshield via videophone.

Study participants confronted a fairly challenging highway scene that involved merging and navigating around unpredictable drivers in other cars.

They found that driving alone was the safest option, in line with previous research. There were significantly fewer collisions when drivers were alone in the simulated car than when they spoke to a passenger in the car with them. Passengers helped drivers find their exits and improved their memory of road signs, but they detracted from overall safety (avoidance of collisions), Kramer said.

As expected, speaking to someone on a cell phone while driving was the most dangerous. 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 most interesting results, however, 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," researcher John Gaspar said. "And this benefit seems to be driven by changes in the way partners talked to the driver."

Seeing the driver and watching what was going on in traffic during the conversation allowed the non-driving partner to stop speaking, for example, when something unexpected occurred on the road, or to point out a situation that might be dangerous, Gaspar said.

"I'm not suggesting people speak on cell phones while driving, but if the driver is speaking to someone who is not in the car, it would be helpful for the conversation partner to have information about what the driver is seeing and doing," Kramer explained.