http://edition.cnn.com/2001/US/08/16...phone.driving/
http://www.nhtsa.dot.gov/people/inju...arch/wireless/
http://www.nsc.org/news/nr012703.htm
all links to studies demonstrating that multitasking (mainly by cellphone use) causes dramatically decreased ability at both tasks. It's safer and easier to do one at a time. Just pull over.
really. cellphone use, eating, reading, any task that divides your attention when driving will seriously affect your driving skill. I was told by my father, the doctor, that with 1 passenger in the car, the chance for an accident rises 200%. By the time you get to 4 passengers, you are 800% more likely to get into an accident than driving alone with a clear head.