3.3.1 "Association between Cellular Telephone Calls and Motor Vehicle Collisions"
Twenty-four percent of participants used their mobile phone in the 10 minutes before the crash.
Using a mobile phone while driving is associated with an approximately four-fold increase in risk compared with not using the phone; this is similar to the risk of driving with a blood alcohol level at the legal limit.
Hand free phones are no safer than hand-held phones.
Younger drivers were found to be at more risk than older drivers.
http://www.cutr.usf.edu/its/mobile_phone.htm