Handheld Vs. Hands

Physical Differences
When you use a handheld cellphone while driving, certain physical actions can potentially cause an accident: dialing a number while driving, and holding the phone while talking. In either case, these actions violate the general safety guideline of keeping both hands on the steering wheel. Additionally, drivers must divert their eyes away from the road to dial a number. Conversely, a hands-free phone uses voice-activated dialing and headsets or a speaker for conversations, and seems, on first glance, to be safer because it eliminates the need to physically hold or operate the phone while driving.
Mental Aspects
Despite the conventional wisdom about hands-free cellphones, both types of phones can divert a driver's mental focus away from the road. According to research done by Ford Motors on a driving simulator, long conversations while driving make it more difficult for a driver to respond to events that occur on the road. The National Highway Traffic Safety Administration, or NHTSA, states that the act of having a conversation is what causes distractions.
Hands-Free Dialing
In addition to the mentally distracting aspect of carrying on a conversation, dialing times for hands-free cellphones are actually longer than the times required to dial on handheld phones. NHTSA states that this longer dialing time negates the fact that hands-free cellphones allow drivers to keep both hands on the wheel.
Statistics
Studies are somewhat inconsistent when it comes to accident rates related to cellphones. However, studies tend to show that both types of phones cause accidents. For example, the New Jersey Department of Transportation did a study of accidents in that state from 2006 to 2008, and found that the number of accidents involving hands-free phones were only 18 percent less than those involving handheld devices. A study by the New York State Department of Motor Vehicles suggests that hands-free cellphones might result in fewer accidents. It found that there were 1,170 crashes involving handheld phones from 2001 to 2006, compared to only 214 for hands-free phones. However, the difficulty in relying on such data is that it does not consider the relative percentage of drivers who use handheld or hands-free devices. Other studies tend to report on overall cellphone statistics instead of distinguishing between the two types of phones.
Laws
State laws that ban the use of cellphones while driving focus on handheld phones. At the time of publication, nine states and the District of Columbia have complete bans on handheld phones. No state prohibits use of hands-free cellphones by all users. However, novice drivers in 30 states and the District of Columbia may not use any phone while driving. A similar ban on hands-free devices applies to bus drivers in 19 states and the District of Columbia.