There is a growing body of research that demonstrates people talking on cell phones while driving are as much a hazard on the road as drunk drivers. Both are equally distracted. That is true of people using hand-held or hands-free cell phone devices.
For that reason, I limit my behind-the-wheel cell phone conversations to near zero and urge all drivers to do the same. Granted, as a team driver, it is easier to manage cell phone calls. When I am driving, Diane answers the phone. Still, for solo and team drivers, talking on the cell phone increases your risk of having an accident.
It is not the same as having a conversation with a person seated in the truck with you. People who know about this stuff say the brain is engaged in a different way and talking on the phone is more distracting than conversing in person.
Like the bumper sticker says, "Hang up and drive."
Here are links to some of many articles/papers/studies that now address this topic:
http://www.psych.utah.edu/AppliedCognitionLab/cdir.pdf
"ABSTRACT—Our research examined the effects of handsfree
cell-phone conversations on simulated driving. We
found that even when participants looked directly at objects
in the driving environment, they were less likely to
create a durable memory of those objects if they were conversing
on a cell phone. This pattern was obtained for
objects of both high and low relevance, suggesting that very
little semantic analysis of the objects occurs outside the
restricted focus of attention. Moreover, in-vehicle conversations
do not interfere with driving as much as cell-phone
conversations do, because drivers are better able to
synchronize the processing demands of driving with invehicle
conversations than with cell-phone conversations.
Together, these data support an inattention-blindness
interpretation wherein the disruptive effects of cell-phone
conversations on driving are due in large part to the diversion
of attention from driving to the phone conversation."
Study: Talkers as Bad as Drinkers
"People who talk on cell phones while driving, even using "hands-free" devices, are as impaired as drunk drivers, researchers said on Thursday.
'If legislators really want to address driver distraction, then they should consider outlawing cell phone use while driving,' said Frank Drews, an assistant professor of psychology at the University of Utah who worked on the study."
Cell phone car accidents:
Cell Phone Car Accidents: Driver Distraction, Auto Driving, Photos, Pictures: Cell Phone User Car Crashes from Car-Accidents.com
A page containing a number of links to a number of reports regarding cell phone distracted drivers and the risks they pose:
News: Driver Distractions
Excerpt from one of them, emphasis mine:
"Washington, D.C. �' The Insurance Institute for Highway Safety (IIHS) released new research concluding that drivers using mobile phones are four times more likely to get into crashes serious enough to injure themselves. IIHS also indicated that hands-free equipment did not reduce chances of injury to drivers. This research, along with other recent studies from the University of Utah and Virginia Tech University, all have similar findings which should impact our public policy discussion about ‘dialing and driving.’
The message is clear: Drivers should not use ANY type of cell phone behind the wheel."