Hands-free kits make drivers even more dangerous
But having a
meatshield passenger reduces the risk
Another study coming out of the University of Utah Applied Cognition Lab has concluded that driving while talking on the phone is a really bad idea, even if using hand-free kit.
The study, published in the Journal of Experimental Psychology (PDF ), concludes that driving while talking on the phone is significantly worse than chatting to a passenger, but if you're going to talk on the phone then having a co-pilot helps.
The study put 96 adults in 48 pairs into a driving simulator and got them to drive for 10 minutes while chatting on the phone, chatting to their partner, and both sitting in silence - presumably following a suitable argument about which route to take. Of those pairs only 41 were used in the analysis, due to technical problems with the simulator.
When chatting on the phone drivers were more likely to slip across lanes, and drive closer to the vehicle in front, not to mention missing their exit as they tried to concentrate on too many things simultaneously. Drivers chatting to a passenger performed much better, perhaps because the passenger could also react to road conditions, even when not involved in the conversation - having a passenger on board helped drivers cope with talking on the phone while driving.
Even more interesting is the analysis of the complexity of words and sentences used. Drivers talking on the phone tended to use longer sentences and words, effectively dominating the conversation, while those chatting to a passenger were happy to take a more passive role in the conversation.
The Applied Cognition Laboratory is doing detailed work, though its statement of objectives  seems counter-intuitive: "The long-term objective of our research is to understand the impact of using advanced in-car technologies on driving performance and traffic safety." Which would be fair enough, if the statement didn't conclude: "We provide a theoretical account for why cell phone use disrupts driving performance." This would seem to indicate they have already reached their conclusions before they start.
Driving while talking on the phone is clearly dangerous, and one mitigates the risk by using hands-free equipment and keeping calls to a minimum. Meanwhile, the far more dangerous pursuit of driving while being an idiot unfortunately remains legal to this day. ®