Crawling along in traffic, you call your co-workers or friends via cell phone, and get caught up. You feel efficient and productive. But in five states you're also a law-breaker, and this legal trend is spreading.

Connecticut, New Jersey, New York, the District of Columbia and the Virgin Islands have passed laws that ban driving while using hand-held phones. So have California and Washington State, where the laws go into effect July 1.

A number of individual cities have also banned them. Utah and New Hampshire include cell phones under their distracted driving laws.

Seventeen states and D.C. now also limit the use of hand-held cell phones by novice drivers, and 15 states and D.C. specifically ban their use by school bus drivers when passengers are present, aside from emergencies.

(Nine states have gone in the other direction, and have acted only to pass laws forbidding local jurisdictions from banning the use of cell phones by drivers.)

Four states (Alaska, Minnesota, New Jersey and Washington) have found it necessary to ban texting while driving, while about a dozen other states are considering the same ban.

Risk factors

Reformers point to studies that show that the risk factor for an accident goes up noticeably if the driver is on the phone.

The increase has been found to range from a factor of 1.3 times higher (found in the so-called 100-car study conducted at Virginia Tech involving video taping the actions of drivers of 100 cars) to 4 (found in Canada and Australia when researchers investigated incidents that led to traffic injuries) to as high as 5 times higher in simulator studies done at the University of Utah, where researchers say the effect equals driving drunk.

Texting would seem to be even more distracting, and the studies bear that out, with the likelihood of an accident rising by a factor of 2.8 in the 100-car study to 8.3 in the Utah study. (The use of hand-held MP3 players and GPS devices can also involve a lot of distracting button-pushing, but so far there has been no backlash against them.)

Talk is dangerous?

The bans on cell phone use by drivers all involve hand-held units. Hands-free calling is invariably exempted. And that leaves the experts groaning, since there is evidence that the act of conversing with someone outside the car is, by itself, dangerously distracting.

"Talking on a phone while driving is dangerous, period, and our advice to drivers is to simply don't do it," said Jonathan Adkins, spokesman for the Governors Highway Safety Association of Washington, DC. "It taxes the cognitive skills of your brain at the expense of the driving at hand, and if the conversation is stressful your reaction time will not be as quick. Also, whoever you are talking with on the phone does not know what is going on around you, whereas someone in the car talking to you is aware of the circumstances."

The Utah studies, for instance, found that drivers who were talking on either a hands-free or handheld phone did worse than those who had a blood alcohol content of 0.08 (the average legal limit.)

Anti-chatter

Cell phones are also getting banned in places where safety is not an issue (if you don't include the possibility of being assaulted by bystanders enraged by all the chatter.)

For instance, France, Germany, Denmark, the United States and Finland have cell-phone free train compartments, sometimes called "zen zones" or "quiet cars" on passenger trains.

But an attempt to enforce such compartments in Stockholm's public transportation was abandoned after 10 months because of massive non-compliance.