So where do state laws stand now?
No state has laws as tough as what the NTSB urges.
For instance, even the nine states that prohibit all drivers from using hand-held phones will allow calls to occur hands-free, such as on speakerphone, according to the Insurance Institute for Highway Safety (IIHS). The five-member NTSB board said bans should extend to hands-free calls.
According to a chart of state laws compiled by the institute, California is the only state with a limit on hands-free use: The state bars young drivers from that activity.
Current laws are tougher on texting. Some 35 states ban the practice of sending and reading text messages while driving, and two more states will join that group over the next four months.
A number of other states have partial texting bans covering new drivers or drivers of school buses and public transit vehicles. Similarly, many states have partial bans on chatting via hand-held phone, on young drivers, or on people like bus drivers.
Beyond the laws themselves lies the issue of enforcement. Traffic-safety experts say many drivers ignore the bans, particularly for texting. "So far it appears that drivers, especially young adults, largely shrug off texting bans," the IIHS says. By comparison, all-driver bans on talking have had more impact on behavior.
The NTSB acknowledged that persuading states to tighten laws and step up enforcement won't be easy.
"We're not here to win a popularity contest," NTSB chairwoman Deborah Hersman said Tuesday. "No e-mail, no text, no update, no call is worth a human life."
A possible ban on hands-free phone use may be particularly controversial for US motorists. Using a head-set or speakerphone currently gives US drivers the chance to do some communicating from their cars while obeying state laws.
Yet safety research by psychologist David Strayer and others at the University of Utah has found that hands-free calls appear to be highly distracting – just as hazardous as driving with a phone in your hand.
The mental distraction is the key problem, they find, rather than whether both hands are free.
One case in point: The NTSB concluded that one probable cause of a 2004 motor coach crash "was the use of a hands-free cell phone, resulting in cognitive distraction; therefore, the driver did not 'see' the low bridge warning signs."
For whatever reasons, some researchers say phone calls are more distracting than conversations with fellow passengers in the car. (For one thing, passengers can help the driver keep tabs on traffic conditions.)
By the way, it's not that other in-car behaviors aren't risks: There may not be laws against it, but other behavior by drivers can be distracting, from looking at maps to eating, or operating a CD player.
Current cell phone bans. The states that bar drivers from using hand-held phones are California, Connecticut, Delaware, Maryland, New Jersey, New York, Oregon, Utah, and Washington. Come January, Nevada will become an 10th state to do this.
Texting. Since most states have bans in place, here's a list of states that will not have a texting ban in place as of next March: Alabama, Arizona, Florida, Hawaii, Idaho, Mississippi, Missouri, Montana, New Mexico, Ohio, Oklahoma, South Carolina, South Dakota, Texas, and West Virginia.