When studies show that a cell phone conversation on its own has a relatively low crash risk, the data isolate the conversation from the physical task of reaching for or dialing the phone itself. Hands-free technology would seem to offer a solution; indeed, many state laws mandate hands-free phone use and proposed legislation concerning text message would ban hand-held use. But these analyses leave out the risks of getting to that phone call, and they also don’t recognize that not all hands-free technology is created equal.
 
The Virginia Tech data show that headset use with a conventional cell phone is not substantially safer than hand-held use. Both methods require manual answering and dialing, which take your hands and eyes off the wheel. Plus, you often wind up fumbling with the headset. Once you take your eyes off the road, you’ve essentially lost all meaningful input -- driving is predominantly a visual task.
 
On the other hand, systems that integrate the phone with the vehicle and use voice-activated technology to control the phone are indeed less risky.  These systems include OnStar, Sync, and integrated Bluetooth capability. They may increase task time as you move through the voice command structure, but they retain eyes-on-road.
 
But once you move beyond manipulating the phone, are you totally safe? This was one of the most contentious points of the first day of the summit. Naturalistic driving studies show little increased crash risk by merely talking on a phone. However, a vast body of other research indicates that the increased cognitive load of cell phone conversations has a big impact on response time and roadway scanning. Multiple safety organizations, like the National Safety Council, advocate no cell phone use at all while driving.
 
Why the disparity in study results? Perhaps the type of questions put to subjects in a simulator study differ from those encountered in real-life driving. Studies often ask subjects to perform math tasks or ask questions that get the subjects personally engaged. Self-regulation of cell phone conversations might avoid thorny issues, saving them for later. Of course, a simulator subject has no option but to be distracted; a driver can opt out of a hard question in a real-life conversation..
 
There are crashes where drivers who were merely talking on the phone -- not actively dialing -- got tunnel vision and ran red lights. (A summit participant lost her family member in just such a crash.) Dr. Horrey noted in his review of the body of study data that cognitive load translates into reduced breadth of scanning and incomplete processing of information.
 
Dr. Thomas Dingus of Virginia Tech noted that it needs to be determined if performance deficiencies in a laboratory setting are amplified or nullified in the real world. The Virginia Tech naturalistic studies so far basically show that if the driver is looking down the road, they snap out of whatever cognitive haze was caused by the conversation and avoid the crash. (Of course, based on other data, it could be argued that they might have better avoided the crash if they were phone-free, maybe by reacting earlier -- but they avoided the crash all the same.)
 
While naturalistic studies have the advantage of measuring drivers in their own cars as they go about their daily driving, there are some considerable disadvantages. These take a long time to conduct and analyze. Plus, they are expensive, limiting the number of participants. There are studies of 2,000 passenger car drivers and 250 truck drivers (who have much more exposure due to miles drive) underway that should increase our understanding of driver behavior. These might better expose the link between the performance detriments shown in the lab and behavior on the road.

So, what can you take away from all of this? In-car conversation with someone sitting in the car with you appears safe, and quite likely is a benefit. Avoiding cell phone use all together in a car removes that particular source of distraction. If you absolutely have to use the phone in the car, an integrated system that keeps your hands and eyes off the phone has a benefit. 

Next from the Distracted Driving Summit: Choosing words wisely

—Tom Mutchler

For more information on distracted driving see our related reports:
Defining the problem: Casting a wide net over driver distraction
Automakers agree to ban
Anti-texting video to scare drivers straight
Using wireless communication devices while driving
Cell phone use and driving laws
Dangers of cell phones while driving
Should cell phone use by drivers be illegal?
Texting while driving
Talking in the slow lane