A preliminary study in 2003 found that drivers talking on cell phones were more impaired than those with a blood alcohol content of .08 percent. The peer reviewed article, recently completed, affirms the earlier conclusions.
We used a high-fidelity driving simulator to compare the performance of cell-phone drivers with drivers who were legally intoxicated from ethanol. When drivers were conversing on either a hand-held or hands-free cell-phone, their reactions were sluggish and they attempted to compensate by driving slower and increasing the following distance from the vehicle immediately in front of them. By contrast, when drivers were legally intoxicated they exhibited a more aggressive driving style, following closer to the vehicle immediately in front of them and applying more force while braking. When controlling for driving difficulty and time on task, cell-phone drivers exhibited greater impairment than intoxicated drivers.
The University of Utah authors summarized the ongoing problem in a companion piece, Why Do Cell Phone Conversations Interfere With Driving?, stating that “as more cognitively engaging technology makes its way into the vehicle, the potential for even more severe driver distraction will increase.”
Just add this to the list of driver distractions that you ask about in your accident investigations.